











- -■ • 
























A. ■>-,. 









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AIR, WATER, AND FOOD 



FROM A SANITARY STANDPOINT. 



BY.» 

ELLEN H. RICHARDS and ALPHEUS G. WOODMAN, 

instructors in Sanitary Chemistry, Massachusetts Institute of Technology. 



"These cannot be taken as sufficient ... in these times when 
every word spoken finds at once a ready doubter, if not an opponent. 
They are, however, specimens, and will serve to make comparisons 
in time to come." — Angus Smith 

"The ideal scientific mind, therefore, must always be held in a 
state of balance which the slightest new evidence may change in one 
direction or another. It is in a constant state of skepticism, knowing 
full well that nothing is certain. "—Henry A. Rowland. 



FIRST EDITION. 
FIRST THOUSAND. 



NEW YORK: 

JOHN WILEY & SONS. 

London : CHAPMAN & HALL, Limited. 

i goo 



3? 






36488 



Library of Conareae 

i ' wu <>£$ Received 
AUG 20 1900 

Copyright entry 

second copy. 

Delivered to 

ORDER DIVISION, 
AUG 22 1900 



Copyright, igoo, 

BY 

ELLEN K. RICHARDS and ALPHEUS G. WOODMAN. 



ROBERT DRUMMOND, PRINTER, NEW YORK. 



3 






CONTENTS. 



CHAPTER PAGE 

I. Three Essentials of Human Existence i 

II. Air: Composition, Impurities, Relation to Human Ltfe 10 

III. The Problem of Ventilation 19 

IV. Methods of Examination 27 

V. Water: Source, Properties, Solvent Power, as a Carrier. 43 
VI. The Problem of Safe Water and Interpretation of Analy- 
ses 62 

VII. Methods of Examination 82 

VIII. Food in Relation to Human Life, Definition, Sources, 

Classes, Dietaries 121 

IX. Adulteration and Sophistication of Food Materials 136 

X. Methods of Food Analysis 146 

Appendices, Tables, Reagents 195 

Bibliography 213 



<> 



s 






AIR, WATER, AND FOOD, 



CHAPTER I. 

THREE ESSENTIALS OF HUMAN EXISTENCE. 

Air, water, and food are three essentials for healthful 
human life. Sanitary Chemistry deals with these three com- 
modities in their relation to the needs of daily existence: 
first, as to their normal composition; second, as to natural 
variations from the normal; third, as to artificial variations — 
those produced directly by human agency with benevolent 
intention, or resulting from carelessness or cupidity. A 
large portion of the problems of public health come under 
these heads, and a discussion of them in the broadest sense 
includes a consideration of engineering questions and of 
municipal finances. This, however, is beyond the scope of 
the present work. 

The following pages will deal chiefly with such portions 
of the subject of Sanitary Chemistry as come directly under 
individual control, or which require the education of indi- 
viduals in order to make up the mass of public opinion 
which shall support the city or state in carrying out sanitary 
measures. 

A notable interest in the subject of individual health as 



2 AIR, WATER, AND FOOD. 

a means of securing the highest individual capacity both for 
work and for pleasure is being aroused as the application of 
the principles governing the evolutionary progress of other 
forms of living matter is seen to extend to mankind. 

Will power may guide human forces in most economi- 
cal ways, and may concentrate energy upon a focal point so 
as to seem to accomplish superhuman feats, but it cannot 
create force out of nothing. There is a law of conservation 
of human energy. The human body, in order to carry on 
all its functions to the best advantage, especially those of the 
highest thought for the longest time, must be placed under 
the best conditions and must be supplied with clean air, safe 
water, and good food, and must be able to appropriate them 
to its use. The day is not far distant when a city will be 
held as responsible for the purity of the air in its school- 
houses, the cleanliness of the water in its reservoirs, and the 
reliability of the food sold in its markets as it now is for the 
condition of its streets and bridges. Nor will the years be 
many before educational institutions will be held as respon- 
sible for the condition of the bodies as of the minds of the 
pupils committed to their care; when a chair of Sanitary 
Science will be considered as important as a chair of Greek 
or Mathematics; when the competency of the food-purveyor 
will have as much weight with intelligent patrons as the 
scholarly reputation of any member of the Faculty. Within 
a still shorter time will catalogues call the attention of the 
interested public to the ventilation of college halls and dor- 
mitories, as well as to the exterior appearance and location. 

These results can be brought about only when the stu- 
dents themselves appreciate the possibilities of increased 
mental production under conditions of decreased friction, 
such as can be found only when the requirements of health 
are perfectly fulfilled. 



THREE ESSENTIALS OF HUMAN EXISTENCE. 3 

Of the three essentials, air may well be considered first, 
although its office is to convert food already taken into heat 
and energy. Its exclusion only for a few minutes causes 
death, and in quantity used it far exceeds the other two.. 
Again, so important is the action of air that the quality of 
food is of far less consequence when abundant oxygen is 
present, as in pure air, than when it is present in lessened 
quantity, as in air vitiated by foreign substances. 

Individual habit has much to do with the appreciation 
of good air, and as our knowledge of the value of an abun- 
dance of this substance in securing great efficiency in the 
human being increases, we shall be led to attach more im- 
portance to the sufficiency of the supply. 

In northern climates air is not free to all in the sense of 
costing nothing, for the coming of fresh air into the house 
means an accompaniment of cold which must be counter- 
acted by the consumption of fuel. A mistaken idea of econ- 
omy leads householders, school boards, and college trustees 
to limit the size of the air-ducts as well as of the rooms. It 
is therefore necessary to emphasize the facts which science 
has fully established, in order to secure the survival of the 
fittest of the race under the present pressure of economic 
conditions, which take so little account of the highest wel- 
fare of the human machine. 

Air, water, and soil are the common possessions of man- 
kind. It is impossible for man to use either selfishly without 
injury to his neighbor and without squandering his inheri- 
tance. Primitive man could leave a given spot when the 
soil became offensive, and neighbors were then too few to 
require consideration; but neither man nor beast could with 
impunity foul the stream for his neighbor who had rights 
below him. The soil is permanent; one knows where to look 
for it and its pollution. Air is abundant and is kept in con- 



4 AIR, WATER, AND FOOD. 

stant motion by forces of nature beyond human control, so 
that, save in the neighborhood of an exceptionally offensive 
factory, man does not often foul the free air of heaven; it is 
only when he confines it within unwonted bounds that it 
becomes a menace. 

Water is the next precious commodity of the three. 
Without it man dies in a few days; without it the soil is bar- 
ren; without it air in motion parches all vegetation and 
carries clouds of dust-particles; without it there is no life. 
As population increases it becomes necessary to collect as 
much of the rainfall as possible, to store it until needed, and 
to use it with discretion. After use it is often loaded with 
impurities and sent to deal death and destruction to those 
who require it later, and yet, in nature's plan, it is the carrier 
of the world, and rightly treated and carefully husbanded 
there is enough for the needs of all. Its presence or absence 
has been the controlling force in determining the habitations 
of men. In its office of carrier it not only brings nourishment 
in solution to the tissues of the human body, but also carries 
away the refuse material. It is a cardinal principle in all 
sanitary reforms to get rid of that which is useless as soon as 
possible. Too little water allows accumulation of waste 
material and a clogging of the bodily drainage system. 

The average quantity needed daily by the human body is 
about three quarts. Of this a greater or less proportion is 
taken in food, so that at times only from a pint to a quart 
need be taken in the form of water as such. 

Next in importance to quantity is the quality, dependent 
somewhat upon the uses to which it is to be put. As a rule, 
the moderately soft waters are the best for any purpose. 
For drinking purposes water must be free from dangers to 
health in the way of poisonous metals, decomposing matters, 
and disease-germs. For domestic use economy requires 



THREE ESSENTIALS OF HUMAN EXISTENCE. 5 

that it should not decompose too much soap. Manufactur- 
ing interests require that it should not give too much scale 
to boilers; for agriculture there should not be too much 
alkali. 

From the nature of things, no one family or city can have 
sole control of a given body of water. Those on the high- 
lands may have the first use of the water, which then perco- 
lates to a lower level and is used by the people on the slopes 
over and over before it reaches the sea to start again on 
its cycle of vapor, cloud and rain, brook and river. Al- 
though receiving impurities each time, there are many 
beneficent influences at work to overcome the evils resulting 
from this repeated use. That which is dissolved from one 
portion of earth may be deposited on another. As the plant 
is the scavenger of the air, withdrawing the carbon dioxide 
with which it would otherwise become loaded, so the water 
has also its plant life, purifying it and withdrawing that which 
would otherwise soon render it unfit for any use. 

Pure water is found only in the chemical laboratory; the 
most that can be hoped for is that human beings may secure 
for themselves water which is safe to drink, which will not 
impair the efficiency of the human machine. 

The importance of the third essential for human life, 
food, and the close interdependence of all three, may be 
clearly shown. Of little use is it to provide pure air and 
clean water if the substances eaten are not)* capable of com- 
bining with the oxygen of the air or of being dissolved in 
the water or the digestive juices; of less use still is it to par- 
take of substances which act as irritants and poisons on the 
tissues which they should nourish, and thus prevent healthful 
metabolism and respiratory exchange. 

And yet a large majority of those who have acquired 
some notion of the meaning and importance of pure air and 



6 AIR, WATER, AND FOOD. 

are beginning to consider it worth while to strive for clean 
water pay not the least attention to the sanitary qualities of 
food; the palatable and aesthetic aspects only appeal to 
them. 

Steam-power is produced by the combustion of coal or 
oil. Human force is derived by releasing the stored energy 
of the food in the body. The delicately balanced mechanism 
of the human body suffers even more from friction than the 
most sensitive machine, and the greatest loss of potential 
human energy occurs through ignorance, carelessness, and 
reckless disregard of nature's laws in regard to food. 

It is necessary to know, first, what is the normal compo- 
sition of a given food-material. This is found by analyses 
of many typical samples. Second, is the sample under con- 
sideration normal? To answer this requires an analysis of it, 
and a comparison of the results with standards. If it is not 
normal, in what way does it depart from the standard both 
in healthfulness and in quality? Third, if a food-substance 
is normal, what are its valuable ingredients and in what pro- 
portions are they to be used in the daily diet? 

In regard to meat, milk, and fish, the sanitary aspect for 
the chemist resolves itself into two questions: Is the sub- 
stance so changed as to become a possible source of poison- 
ous products? Or has anything in the nature of a preserva- 
tive been added to it? If so, is it of a nature injurious to 
man? 

There is, however, a great range of quality in some of the 
most abundant foodstuffs, such as the cereals, especially in 
the nitrogen content. This is most important to the vege- 
tarian and to institutions where economy must be practised. 
The following variations in the composition of leading cereals 
will illustrate: 



THREE ESSENTIALS OF HUMAN EXISTENCE 7 



•m *~~ Nitrogenous Crude Carbo- Flhr . 

Water - Substance. hat. hydrates. Flbre - 



Ash. 



Oats, maximum 20.80 18.84 10.65 64.63 20.08 8.64 

" minimum 6.21 6.00 2. 11 48.69 4.45 1.34 

" American hulled. 12. 11 13-57 7-68 63.37 1.30 2.03 

Corn, maximum 22,20 14.31 8.87 52.08 7.71 3.93 

" minimum 4-68 5-55 1-73 72-75 0.99 0.82 

One sample of wheat flour may contain 14 per cent, of nitro- 
genous substance, another may yield only 9. A day's ration, 
500 grams, will give 70 grams of gluten, etc., in the one 
case and only 45 in the other. This difference of 25 grams 
would be a serious factor in the dietary of an institution 
where little additional proteid is given, and it alone might 
be the cause of dangerous under-nutrition. 

The next step would naturally be to determine how 
definitely these varying percentages mean varying nutrition. 
To this end a study of vegetable nitrogenous products in 
their combination or contact with cellulose, starch, and min- 
eral matter is needed. Much work remains to be done 
before these questions can be even approximately answered. 

At the low cost of one cent a pound, common vegetables 
yield only about one-fifth as much nutriment as one cent's 
worth of flour, yet they contain essential elements and de- 
serve to be carefully studied. 

Dried fruits and nuts are much undervalued as articles of 
food, as are rice and lentils. (See table, page 130.) 

The discussion of food values will be found in Chapter 
VIII. 

Probably the widest field for the sanitary chemist to-day 
is the study of the so-called predigested foods, infant foods, 
" hygienic " preparations, two-minute cereals, and the count- 
less proprietary packages, which, designed to meet the de- 
mand for quick results, prove traps for the unwary. 

Therefore the sanitary aspect of food demands a study 



8 AIR, WATER, AND FOOD. 

of normal food and food value even more than of adulterants 
or of poisonous food, ptomaines and toxines. The cultiva- 
tion of intelligent public opinion is most important, and each 
student should go out from a sanitary laboratory a mission- 
ary to his fellow men. That is, the office of a laboratory 
of sanitary chemistry should be so to diffuse knowledge as 
to make it impossible for educated people to be deluded by 
the representations of unprincipled dealers. Freedom from 
superstition is just as important in this as in the domain of 
astronomy or physics. So long as chemists are employed 
by manufacturing concerns in making adulterated and 
fraudulent foodstuffs, so long must other chemists be em- 
ployed in protecting the people until the public in general 
becomes wiser. A part of the common knowledge of the 
race should be the essentials of healthful living, in order that 
the full measure of human progress may be enjoyed. 

There is needed a greater respect for food and its func- 
tions in the human body, a better knowledge of its effect on 
the daily output of energy, its absolute relations to health 
and life, and the enjoyment of the same. The familiarity 
with these facts which is given by a few hours' work in the 
laboratory will make a lasting impression and will enable the 
student to benefit his whole life, even if he never uses it pro- 
fessionally. It is purely scientific knowledge, just as much 
as that derived from a study of the phases of the moon or the 
formulas of integration. 

The variety of operations in such work, calling for great 
diversity of apparatus and methods, is an educational factor 
not to be overlooked in laboratory training. 

For all detailed discussions and methods the reader is 
referred to such works as those of Wiley, Allen, Blythe, etc., 
but for the student who needs to study, as a part of general 
education, only typical substances, and such methods as can 



THREE ESSENTIALS OF HUMAN EXISTENCE. 9 

be carried out within the limits of laboratory exercises in a 
college curriculum, the following pages are written. Not 
enough is given to frighten or discourage the student, but 
enough, it is hoped, to arouse an interest which will impel 
him at every subsequent opportunity to seek for more and 
wider knowledge. 



CHAPTER II. 
air: composition; impurities; relation to human 

LIFE. 

The average adult human being makes about eighteen 
involuntary respirations per minute. The tidal volume of 
air is from 300 to 500 cubic centimeters (30 cu. in.), about 
2800 cubic centimeters (170 cu. in.) remaining in the lungs 
unless voluntarily expelled by deep breathing. The total 
volume expelled is often called the vital capacity, and is about 
3400 cubic centimeters for men and 2500 for women. Even 
when at rest a volume of 7000 to 12,000 liters (250 to 420 
cu. ft.) of air passes through the lungs of each individual in 
twenty-four hours. Under conditions of exercise more or 
less prolonged or violent this volume may be doubled. The 
composition of the normal inspired air by volume is approxi- 
mately: nitrogen and argon 79 per cent., oxygen 20.9 per 
cent., other constituents 0.1 per cent. The air as it leaves 
the lungs contains nitrogen 79.5 per cent., oxygen 16.0 per 
cent., carbon dioxide 4.4 per cent., and is saturated with 
water-vapor. There has therefore taken place an inter- 
change of gases (called the respiratory exchange), by which 
oxygen has passed into the fluids of the body, and carbon 
dioxide into the air contained within, the lung-cells.. Only 
about one-fifth of the total oxygen is abstracted during each 
tide. 

If the composition of the inspired air varies from the 



air: relation to human LIFE. II 

normal, this exchange is disturbed, owing to the difference 
in gaseous pressure and in rate of absorption which this 
variation causes. So delicate is the balance of the active 
forces that serious disturbance of the functions of the living 
organism occurs if the percentage of oxygen is lessened by 
one or two tenths, or if the pressure is raised or lowered by 
a fraction of an atmosphere. It is true that, like a tree 
bending before the wind, the organism soon adapts itself to 
changed circumstances, provided the change is not too great 
nor too suddenly made; but, like the exposed tree, the living 
being is never quite so vigorous and symmetrical as it would 
have been without the effort to overcome disadvantageous 
conditions. 

That a permanent or habitual lowering of the oxygen in 
inspired air must be harmful will be readily seen from a con- 
sideration of the office of this gas in the body. To Lavoisier 
and Laplace we owe the knowledge that animal heat is de- 
rived from a process of combustion. Lavoisier held, how- 
ever, that the seat of this combustion was in the lungs, and 
it is to Pfliiger and his pupils that we are indebted for the 
proofs that it is in the tissues themselves, while the lungs 
serve as a clearing-house or centre of exchange. 

By the union of the oxygen with the substances found in 
the tissues and brought to them by the circulating fluids of 
the body from the digested food, the heat necessary for the 
life and work of the body is produced. This heat is needed 
to keep the tissues at the temperature at which they can best 
accomplish their work, to give mechanical power for the in- 
voluntary action of heart and lungs, for the processes of 
assimilation, and to furnish the energy for all voluntary work 
and thought. Thus both water and food are intimately con- 
cerned in the processes in which air is an essential factor. 
The statement made in the first sentence of Chapter I is 



12 AIR, WATER, AND FOOD. 

therefore justified, namely, that air, water, and food together 
are three essentials of human existence. A certain relation 
between the three means health, and any disturbance of this 
relation means unhealth, by which term may be designated 
a condition of less than perfect health not yet so serious as 
to be called sickness. 

Air being a mere mixture of the gases nitrogen and oxy- 
gen, in no definite atomic proportions, and carrying varying^ 
amounts of other substances, gaseous and suspended parti- 
cles, no definite composition can be given. The difference 
between the air over sea or forest plateau and that of city 
streets or of crowded tenements seems only slight if expressed 
in per cent. From 20.98 per cent, of oxygen in the first to 
20.87 an d 20.60 in the last; from .022 per cent, of carbon 
dioxide in the purest air to .045 in cities and .33 in rooms, are 
the common variations; and yet the effect of these apparently 
sma 1 l differences on human beings subjected to them is very 
noticeable. It is customary to enhance these differences by 
expressing the results in parts per 10,000. 

That the carbon dioxide is of itself a disturbing factor is 
indicated by the observed fact that air which has had the per 
cent, of oxygen reduced by combustion to a point at which 
a candle will no longer burn may be made again a supporter 
of combustion by the removal of the carbon dioxide. 

A practical application of this principle is made in the 
devices used in diving and in entering mines filled with irre- 
spirable gases. 

There is a sensible effort in breathing, and a feeling of 
discomfort is usually experienced, if the carbon dioxide ac- 
cumulates to ten times the normal amount, or 40 parts per 
10,000 instead of 4. This is probably due to its solubility 
and to its interference with the respiratory exchange, since 
the interchange of gases is influenced by their " partial pres- 



AIR: RELATION TO HUMAN LIFE. 1 3 

sures." Each gas forming part of a mechanical mixture 

exerts a partial pressure proportional to its percentage of the 

mixture. For example, if atmospheric air, containing 20.81 

per cent, of oxygen, is at 760 millimeters barometric pres- 

20.81 
sure, the partial pressure of the oxygen would be X 

760=158.15 millimeters. The following partial pressures 
of oxygen and carbon dioxide in inspired air and in the lung- 
cells show the extent of variation in different parts of the 
respiratory tract: 

Inspired Air. Lung-cells. 

Oxygen 158.15 mm. 122 mm. 

Carbon dioxide 0.30 mm. 38 mm. 

Gas will always tend to diffuse from the region of high- 
est to that of lowest pressure. Hence the reason for the 
great influence of pressure in causing the diffusion of oxygen 
from the inspired air into the lung-cells and for the converse 
movement of carbon dioxide. That variation in pressure 
has much to do with the discomfort is shown in the so-called 
mountain-sickness, experienced at high altitudes in rarefied 
air, and in the so-called caisson-disease, developed in men 
working in compressed air. If the passage from the caissons 
to the open air is made gradually, there is little trouble, but 
a quick change is often dangerous. A sort of mountain- 
sickness is experienced by many on entering a close room 
from the outside air. Usually this passes away in a measure 
as the organism accommodates itself to the new conditions. 
Even if the symptoms are not severe, there is a dulness or 
an irritability which is not conducive to the best apprehen- 
sion of a difficult subject or to the fullest enjoyment of an 
entertainment. 

This lessening of mental capacity is especially to be de- 



14 AIR, WATER, AND FOOD. 

plored in the case of school-children, who are at an age when, 
respiration is most frequent and the need of pure air the 
greatest, and also when economy of effort is most demanded. 

It has been said that from the study of the physiological 
effects of close air it seems to be indicated that the evil is 
due to the change in the respiratory quotient and to the con- 
sequent change in blood-pressure, which interferes with the 
circulation. The respiratory quotient is obtained by divid- 
ing the volume of carbon dioxide given off by that of the 
oxygen absorbed, and indicates how much of the oxygen has 
combined with carbon to form carbon dioxide, since one vol- 
ume of oxygen combines with cafbon to form one volume of 
carbon dioxide. The rate of exchange is influenced by- 
questions of pressure, exposure, temperature, and water- 
vapor or moisture, muscular activity, and the like. 

Water-vapor is the most variable constituent, due to the 
changing capacity of air for moisture at different tempera- 
tures and to the character of the earth's surface. Whether 
over land or water, cultivated or forest region, air at o° C. 
contains only 4.87 grams of water per cubic meter, while air at 
6o° F. (15 C.) can take up 12.76 grams, and at 90 F. holds 
33.92 grams. Since the human body is constantly giving off 
moisture from skin and lungs, and since this exhalation is an 
important factor in the bodily economy, the presence of ex- 
cessive moisture in the air exercises a decided effect. 

On clear, invigorating days the moisture in the air may- 
be only 30 or 50 per cent, of that required for complete satu- 
ration at the given temperature, and although the ther- 
mometer reading may indicate 85 ° F. on a hot day, little 
discomfort follows; but let the humidity rise to 90 or 95 per 
cent, while the temperature remains the same, and oppres- 
sion, restlessness, or languor results. Much the same effects 
are seen in the case of close rooms and crowded halls. The. 



air: relation to human life. 15 

watery vapor given off (about 20 grams per person per hour) 
soon saturates the air, and the consequent drowsiness and 
headache usually attributed to carbon dioxide will be felt; 
while if this moisture is removed, the same proportion of 
carbon dioxide would hardly inconvenience the occupants. 
A relative humidity of 60 per cent, is said to be the most 
comfortable for house temperature. 

In normal man, exposure to cold increases the respiratory 
exchange; but if he represses shivering and keeps still by 
force of will, it apparently does not. Politely sitting still in- 
creases the probability of taking cold. A high temperature 
lessens the production of carbon dioxide and therefore saves 
food. This may in part account for the oppressiveness felt 
by well-fed and warmly clothed persons in public places none 
too warm for those with a more restricted diet. 

Muscular activity increases respiratory exchange and 
causes a demand for food. A class of students passing across 
the campus, up several flights of stairs, into a lecture-room 
vitiate the air for the first ten minutes at a rate higher by 
one part of carbon dioxide per 10,000 than half an hour later. 
The exchange is also stimulated by a meal Not only the 
oxidation of the food itself, but the muscular activity of the 
alimentary canal and probably other accompanying activities 
call for an expenditure of energy which is supplied by in- 
creased heat production. 

Sodium sulphate is said to increase the various respira- 
tory activities, and some have held this fact to be one reason 
for the beneficial effects of certain mineral waters. 

The amount of carbon dioxide expired is estimated by 
Pettenkofer at .006 to .012 cubic foot per pound of body 
weight, according to the degree of exertion. Rubner con- 
siders that, in general, metabolic processes depend also upon 
the proportion of superficial area to the total volume of the 



l6 AIR, WATER, AND FOOD. 

body, hence the smaller the animal the greater the surface to 
the whole mass. Children give off in proportion to their 
body weight about twice as much carbon dioxide as adults. 
Another estimate gives the output of carbon dioxide as 
.0027 gram per hour per square centimeter of surface. 

Ammonia is also a constant component of the air of in- 
habited places and is washed out by rain and snow, as will 
be shown in Chapter VI. 

Of the occasional impurities, probably the most fatal is 
carbon monoxide arising from leaking gas-fixtures or de- 
fective furnaces. This gas has 250 times the affinity for 
haemoglobin and therefore forms with it a more stable 
compound than does oxygen, and hence its presence causes 
a deficiency of the latter gas in the blood, giving symp- 
toms like those observed in mountain-climbing or bal- 
loon ascensions. When the blood-corpuscles become about 
one-third saturated the effect becomes sensible; but if the 
quantity of gas is considerable, the symptoms are hardly 
noticeable before insensibility occurs. For this reason, glow- 
ing charcoal and open gas-jets are the favorite forms of 
cowardly self-destruction. 

In the neighborhood of factories, smelting-works, ore- 
heaps, and of cities burning soft coal there is a noticeable 
amount of sulphurous and sulphuric acids, sometimes so con- 
siderable as to destroy vegetation. 

In places where gas is burned, oxides of nitrogen are 
formed in small quantity, the effect of which is known to be 
harmful. Minute quantities of hydrogen sulphide and of com- 
pounds of carbon and hydrogen and of other gases may be 
present, especially in houses with defective plumbing or in the 
neighborhood of barns, cesspools, and filthy back yards. 
These may reach dangerous proportions, but, like carbon 



air: relation to human life. 17 

monoxide, should not be permitted in or near any well-regu- 
lated household. 

Soot, being insoluble, accumulates in the lungs, as a post- 
mortem examination of persons who have lived for some time 
in a smoky city proves; nevertheless no definite ill effects 
have been as yet attributed to this cause. This again con- 
firms the inference that it is the gaseous constituents, and the 
varying temperature and pressure, which seriously affect the 
respiratory exchange 

The following results, obtained on the air of a large man- 
ufacturing city, will be of interest in this connection:* 

GRAMS PER 1,000,000 CUBIC METERS OF AIR.f 
Soot. H 3 S0 4 . FreeNH 3 . Alb. NH 3 . HNO,. HN0 2 . 

IOOO to 40000 7000 to 63000 1 IOO to 1000 97 to 557 45 to 1063 O to 155 

1 Partly H a S0 3 . 

It is probable that much of the danger ascribed to sewer- 
air arises from other causes. Since the atmosphere in sewer- 
pipes is always moist, the only probable source of organisms 
is the splashing of the water. Only about one-half as many 
organisms have been found in the air a'bove flowing sewage 
as in out-door air. Professor Carnelley and Dr. Haldane 
found only one-half as much carbon dioxide and one-third 
as much organic matter in such air as in that of t'he streets 
above. 

Beyond individual control, and in a measure beyond gen- 
eral control, there exists suspended matter in the air: fine 
volcanic dust, pollen, spores of moulds and algae, dried bac- 
teria, diatoms, small seeds of plants, soot and the finely 
pulverized earth from roads and cultivated and barren lands. 
To this portion of the air we owe beautiful sunsets and dis- 
agreeable fogs. To it many affections of the throat and 

* Mabery: /. Am. Chem. Soc, 17 {1895) 105. 

f See also Bailey: " The Air of Large Towns," Science, Oct. 13, 1893. 



1 8 AIR, WATER, AND FOOD. 

eyes are due, and by it disease may be transmitted. Some: 
kinds of dust lodge in the air-cells and by irritation render 
the individual liable to disease, as statistics of the mortality 
in dust-producing trades show. In the air of houses this. 
impurity increases a thousand-fold by means of the wear of 
furnishings and the accumulation on them of deposited par- 
ticles, by means of furnace-ashes and dried debris of all 
kinds. Only recently have the dangers of this part of the 
air we breathe been distinctly pointed out. 

Aitken * estimated that a cubic inch of air may carry 
2000 dust-particles in the open country, 3,000,000 and more 
in cities, and 30,000,000 in inhabited rooms. Among these 
millions there may be found from ten to several hundred 
micro-organisms, moulds, and bacteria, and, under certain 
conditions, pathogenic germs. 

As methods of culture become more satisfactory and tests 
more universal, it may be demonstrated that many old or 
long-inhabited buildings furnish several varieties of patho- 
genic germs constantly to the air. 

According to some authorities, the most dangerous con- 
tamination of the air is the " crowd-poion," or organic 
matter given off with the carbon dioxide and moisture in the- 
breath. References will be found in the bibliography to dis- 
cussions of the subject. No evidence has ever been found 
in the course of investigations in this laboratory, covering 
a period of fifteen years, that the healthy human lung gives off 
any toxic substance. 

* Nature, 31 {1870), 265; 4 1 (iSSo), 394. 



CHAPTER III. 



THE PROBLEM OF VENTILATION. 



From the preceding chapter it will be seen how impor- 
tant is the purity of the air to human well-being, and how 
essential is the diffusion of the knowledge of the methods 
by which it can be secured. It is often said that artificial 
ventilation is a modern necessity. Remains of aqueducts 
and sewers have testified to the sanitary intelligence of his- 
toric peoples, but the ventilating fan does not seem to have 
been included, although natural ventilation by shafts and flues 
has been practised since man came out of cave-dwellings. It 
is true that customs have changed as to many items of daily 
life. In cities more people live on an acre of ground, thus 
fouling the air above and the ground beneath ; more factories 
are belching smoke; more coal is burned; houses are built 
with smaller rooms and less pervious walls; schools and 
lecture-halls are more crowded; people are better fed, con- 
sequently there is more garbage; streets are macadamized, 
allowing finely ground particles to fill the air with every puff 
of wind; gas-pipes traverse the walls of every house and 
pass under every street; carpets, draperies, and much passing 
in and out cause an accumulation of dust unknown fifty 
years ago. Kerosene lamps require more oxygen than many 
candles. Besides, people are becoming less hardy and more 
sensitive physically, so that well-ventilated living-spaces are 
a modern necessity if human efficiency is to be maintained. 

19 



20 AIR, WATER, AND FOOD. 

As we have seen, the air of open spaces presents only 
very slight variation at the same level or for several thousand 
feet above it. The movement of the air caused by the wind 
is usually so rapid, and the reservoir of air for many miles 
above the earth is so immense in comparison with the thin 
vitiated layer, that there are only to be considered enclosed 
spaces in which human beings remain for a period of time. 

To supply the 7000 to 12,000 liters (250 to 430 cubic feet) 
of tidal air per person in maximum purity, there must be. 
brought to the person at rest some 1800 cubic feet of air per 
hour. If he were in an air-tight chamber 12 feet square and 
8 feet high, a man would reach the limit of purity in 38 
minutes; but no ordinary room is air-tight, and when the 
difference between inside and outside temperature is consid- 
erable, a rapid exchange is taking place even with doors and 
windows shut. 

To secure the passage of this large volume of air through 
a small space without causing a draft that will be objected to 
by the abnormally sensitive victim of modern luxurious 
habits is the problem of ventilation — one not yet satisfactorily 
solved. 

The sanitary engineer is expected to design the appara- 
tus and to aid the architect in so placing and proportioning 
flues, inlets, and outlets as to accomplish the desired results. 
Unfortunately it is too common, especially in the case of 
school and college buildings, to economize in the first cost 
by dispensing with the services of the expert and to leave to 
the builder and " practical " architect all such details. In 
any case, it often becomes necessary to call in the chemist to 
prove the need of reform, or to show by the composition of 
the air whether or not the ventilating plant is doing its work 
efficiently. 

The sanitary inspector, whose business it is to decide 



air: the problem of VENTILATION. 21 

upon the legal questions connected with tenements and fac- 
tories, must often rely upon chemical examinations of the 
air. The validity of these depends not only upon the per- 
fection and delicacy of apparatus and methods used, but also 
upon the judgment and intelligence with which the samples 
are taken. 

Many errors in the construction of buildings have been 
perpetrated because of an ignorance of the physical proper- 
ties of air and, consequently, a mistaken notion of the be- 
havior of a vitiated atmosphere. The lecturer on popular 
science who some forty years ago enlightened (?) the com- 
munity on the chemistry of daily life was accustomed to use, 
as a striking illustration, a glass jar in which a small lighted 
candle was instantly extinguished on pouring into the jar a 
tumblerful of carbon dioxide which had been collected for 
the purpose. The inference was plain: carbon dioxide was 
heavier than air, therefore it falls to the floor and must be 
allowed to flow out as if it were a stream of water. Further 
confirmation of this inference was found in the frequently 
observed fact that a candle lowered into a well often went 
out just before the water was reached. 

Hence for many years the habits of thoughtful persons 
were formed on a belief in the heaviness of carbon dioxide or 
" bad air," and in its tendency to go to the bottom of the 
room and into any holes it could find. This is only another 
instance of danger in half a truth. When do we find cold 
carbon dioxide generated in living-rooms? And how warm 
must the gas be in order to be lighter than the ordinary air? 
How quickly does diffusion take place? Until within a very 
few years the almost unanimous belief among the so-called 
educated classes was that the bad air could be let out by 
opening a window at the bottom, and, in spite of the lessons 
which might have been learned by any observant person in 



22 AIR, WATER, AND FOOD. 

hanging pictures or Christmas greens, the common practice 
in private houses, churches, and schools is to open the win- 
dows at the bottom. 

All ordinary vitiation of the air proceeds from a heated 
source. Human breath and warm air are lighter than cold 
air and rise even with their burden of carbon dioxide. It is 
only when they impinge on a very much colder surface, as on 
the window-pane on a very cold day, that they become suffi- 
ciently chilled to fall without mixing with the neighboring 
air. The freedom with which the gases of the air mix, as 
well as the rapidity of the action, may be illustrated in a 
variety of ways. Open a bottle of any volatile and pungent 
substance, as ammonia or hydrogen sulphide, in one corner 
of a room, and almost instantly it may be perceived in the 
most distant part. 

In natural ventilation we have only to avail ourselves of 
these characteristic properties of gases; and whether we wish 
to get rid of the light gases escaping from furnace, stove, or 
gas-pipe, or of the specifically heavier carbon dioxide, or of 
the most dangerous dust, we must furnish an outlet at the 
place to which the fleeing enemy first arrives, lest it turn and 
rend us for our ignorance. 

It is usually sufficient to furnish this opportunity, the 
current caused by this willing escape drawing in sufficient 
fresh air to take its place except in very crowded rooms, and 
even these might be so ventilated provided the whole roof 
were one large ventilating flue. If, however, the air is to be 
drawn from the bottom of the room, its unwilling current 
must be pulled by a superior force, as by an open fire on the 
hearth, which heats the air above it so that, in rushing into 
the free air above, it draws after it all things movable within 
reach. Then, indeed, even the top of the room becomes 
quickly cleared and no corner can escape; but if the fire be 



air: the problem of ventilation. 23 

long gone out and the chimney cold, the reverse takes place 
and cold, heavy air sinks to the floor, helping to confine the 
had air at the top of the room. 

What the cold chimney cannot accomplish the mechani- 
cally driven fan can do, namely, by a slight compression 
force a draught even up a cold chimney. In this case the 
very unwillingness of the air to take the prescribed path 
helps in the result as water forced through a mill-wheel de- 
velops mechanical work. The warmed fresh air forced in 
near the top of the room loses its velocity as it mingles with 
that already present, and finds its way along the line of least 
resistance to the opening provided at the bottom of the 
room, into the flue, but only in case there is no easier way. 

Open doors or windows interfere with the prescribed 
course, and blindness to this fact on the part of the occupants 
of mechanically ventilated buildings has caused unjust com- 
plaints of the system. The necessity of regulating the con- 
sumption of fuel and admission of fresh air in accordance 
with variations of temperature, as well as the great care and 
trouble this involves, renders the " natural " system of ventila- 
tion practicable only in less crowded dwelling-houses where 
intelligence can control the varying factors. For schools, 
lecture-halls, or any enclosed spaces occupied by numbers of 
persons at one time, some form of mechanical ventilation 
offers the only hope of good air in cold climates. What 
form that shall take is for the engineer to decide. The chem- 
ist's part is to devise means of readily determining whether 
the persons in charge of the apparatus are using it to gain 
the results designed by the expert. 

As a test of how nearly practice approaches the theoreti- 
cal value, carbon dioxide is taken as the indicator, since it is 
present in a thousand times larger quantitv than any other 
impurity and since it is easily determined. If the air has 



24 AIR, WATER, AND FOOD. 

only the normal amount of carbon dioxide, it is but rarely 
that it contains enough of anything else to be harmful. The 
presence of hydrogen sulphide or of coal-gas is betrayed by 
the odor. Where the gas-supply is " water-gas," contain- 
ing 30 to 40 per cent, of carbon monoxide, there is greater 
danger; but if legal restrictions are complied with, the pres- 
ence of this can be detected in the same way, viz., by the 
odor. 

Danger may also arise from the presence of so-called 
" sewer-gas," which, however, is not a single gas, but a most 
complex and variable mixture of the more volatile products 
of decomposition. For the detection of " sewer-air " chemi- 
cal tests are of little value, since it contains no constituent 
in sufficient quantity and with sufficient regularity to 
serve as an index of its presence. Ill-smelling gases are 
given off only when sewage is about eighteen hours old, 
hence dirty house-pipes are the chief cause of foul air. The 
delicate sense of smell is of value here. Indeed, an edu- 
cated nose is most essential in all examinations of house- 
air. " Crowd-poison," if it exists, keeps company with the 
increase of the products of respiration, and if the incoming 
air is strained or taken from a place free from dust, the par- 
ticles added to the air which is in the rooms will also be re- 
moved with the carbon dioxide. 

From nearly all points of view, carbon dioxide is an indi- 
cator of the efficiency of ventilation, especially if combined 
with observations of temperature and moisture. It is an in- 
dicator also readily understood and accepted by the public. 

The principles of ventilation may be readily illustrated to 
a class by means of simple apparatus. Such an apparatus, 
using candles and designed to illustrate the section of an 
ordinary room, is shown in Fig. 1. 

In testing the efficiency of ventilation of any room or 



AIR: THE PROBLEM OF VENTILATION. 



25 



building, it is necessary to determine first the direction of the 
air-currents, for there can be no ventilation without currents. 
If the architect who designed the building, or the engineer 
who advised the architect, is responsible, then the chemist 
has only to follow directions in taking the samples; but fre- 
quently the chemist, as well as the sanitary engineer, is called 




Fig. 1. — Apparatus to Illustrate the Principles of Ventilation. 

upon to make tests of rooms and buildings of which no plans 
are available. 

In the examination of such rooms, then, the position of 
flues or conduits, both inlets and outlets, which were intended 
to convey air or which serve without such intention, should 
first be located. Possible avenues of ingress and egress by 
means of loose windows, cracks around doors, etc., are to be 
considered. When there is great difference of temperature 
between outer and inner air, these allow of quite rapid change 
of air. Some means of rendering visible these currents is de- 
sirable, such as smouldering paper, magnesium powder, or 
fumes of ammonium chloride. 



26 AIR, WATER, AND FOOD. 

When the direction and intensity of these air-currents 
have been determined, the places from which the air-samples 
are to be taken may be chosen. It will be evident in what 
part of the room stagnation occurs and where eddies are 
formed, also where the air escapes. 

In a room or building without artificial ventilation the 
air-currents are seen to be ascending until they become 
chilled, when they fall. An empty room will not show so 
decidedly the rise of air-currents as will an occupied one in 
which the vitiated air, being much warmer, rises more rap- 
idly and cools less quickly. In taking the samples all acci- 
dental means of contamination must be avoided and the 
occupants must be quiet, for the moving of persons causes 
disturbance in the air-current. There is room for great in- 
genuity in this part of the examination, as circumstances 
greatly modify the method of procedure. A fa'r sample, or 
a sufficient number of samples to give a fair average, must 
be taken. 

Having secured and analyzed the samples of air, the de- 
cision as to the efficiency of ventilation must be rendered. 

If the room examined is a study- or recitation-room, the 
stratum of air at the level of the students' heads should not 
contain over 8 or 9 parts per 10,000 of carbon dioxide, should 
not show a temperature of over 70 ° F., nor a humidity of 
over 35 or 50 per cent., and these conditions should be main- 
tained for hours at a time. 

For lecture-halls and spaces occupied for on 1 y one hour 
at a time, with ample time between occupation, it is admis- 
sible to allow 9 to 11 parts. If fan ventilation is used, the 
outlet should give the average degree of contamination. If 
no system is used, the air at the top of the room is first 
vitiated; only at the end of twenty minutes to half an hour 
do the lower layers begin to show it, 



CHAPTER IV. 

ANALYTICAL METHODS. DETERMINATION OF CARBON 

DIOXIDE. 



General Statements. — The methods of determination all 
rest upon the property which the " caustic alkalies," the 
hydroxides of potassium, calcium, and barium, possess of 
uniting with carbon dioxide and forming stable compounds. 

Where it is necessary to absorb large quantities of the 
gas in a slight volume of solution, potassium or sodium hy- 
droxide is used. For nearly 
all of the " popular tests " cal- 
cium hydroxide, lime-water, 
is used because of its harmless 
nature and the ease with 
which it can be obtained from 
the corner drug-store, or from 
the quicklime procured fro:u 
the mason's barrel. For vol- 
umetric methods barium hy- 
droxide is generally preferred, 
because of the less solubi.ity 
of the barium carbonate, it 
being only about two-thirds 
as soluble as the calcium salt. 
The very avidity with which 
these substances take up car- 
bon dioxide is a hindrance to 
the preparation of standard solutions in an atmosphere 




Fig. 2. 



2$ 



AIR, WATER, AND FOOD. 



already rich in it. When once prepared the solution must 
be preserved with especial care, since contact with the hands 
or a whiff of the breath will reduce its strength and vitiate 
the results. All such solutions are best kept in bottles well 
protected from the air by tubes filled with soda-lime and de- 
livered from a burette, as in Fig. 2. 

For some of the methods it will be found advantageous 
to have the solution measured for each test by means of an 
automatic pipette, as shown in Fig. 3. 
This can be attached directly to a liter 
bottle containing the stock solution, and, 
if placed in a suitable case to prevent in- 
jury, may be easily carried from one 
place to another. This is especially con- 
venient for several of the " popular 
tests." 

Pettenkofer Method. — The method 
for the determination of carbon dioxide 
which has been found most satisfactory 
in accurate work is a modification of the 
Pettenkofer method.* 

Principle. — In principle this consists in absorbing the car- 
bon dioxide from a known volume of air in barium hydroxide 
solution and titrating the excess with standard sulphuric acid. 
It is essential for the complete absorption of the carbon dioxide 
that the barium dioxide be largely in excess so that not more 
than one-fifth of it is neutralized; furthermore, the absorbing 
solution must be shaken up with the air for a considerable 
time. 

Collecting the Samples. — The samples are collected in four- 
or eight-liter bottles, the volume of which is accurately 

* Pettenkofer: Annalen, 2, Supp. Band {1862), p. 1. Gill: Analyst, 17 
(1892), 184. 




Fig. 3. 



air: analytical methods. 29 

known, the bottles having been calibrated by weighing them 
filled with water. These bottles are provided with a rubber 
stopper carrying a glass tube over which a rubber nipple is 
slipped. They are filled with the air to be tested by means 
of a pair of nine-inch blacksmith's bellows, fitted with valves 
so arranged as to draw the air out of the bottle. The bel- 
lows is connected with a three-quarter-inch brass tube reach- 
ing nearly to the bottom of the bottle; fifteen or twenty 
strokes should be sufficient to replace the air in a four-liter 
bottle. At the time of collecting the samples the following 
observations should be recorded: Room, date, time, weather, 
place in room, number of people present, number of gas-jets or 
lamps burning, condition of the doors, windows, and transoms; 
in short, everything which would tend to affect the amount of 
carbon dioxide in the air, or to cause currents or eddies. The 
bottles should be distinctly labelled and their volumes re- 
corded. If the temperature at the point where the samples 
are collected should be essentially different from that of the 
laboratory, the bottles should be allowed to stand in the 
laboratory for half an hour or until they have attained its 
temperature. 

Directions for Laboratory Work. — The solutions of barium 
hydroxide and sulphuric acid which are used are approxi- 
mately of equal strength; but since it is impracticable to pre- 
pare exact solutions of barium hydroxide and to keep them 
without change, the exact value of the barium hydroxide so- 
lution must be found by titration against the standard 
sulphuric acid, which is made of such a strength that 1 cubic 
centimeter is equivalent to exactly 1 milligram of C0 2 . 
This standardization, as well as the subsequent titration, is 
best made in a small flask to lessen the error from absorption 
of carbon dioxide from the air. It will be found most gen- 
erally satisfactory to measure into the flask about 25 c.c. of 



30 AIR, WATER, AND FOOD. 

the barium hydroxide, add a drop of phenolphthalein solu- 
tion, and titrate with the sulphuric acid to the disappearance 
of the pink color. In all cases the first end-point should be 
taken as the correct one, because the pink color will some- 
times return on standing. This is due to the presence of 
minute quantities of potassium or sodium hydroxide in the 
solution. The alkali sulphates will react with any barium 
carbonate which may be suspended in the liquid with the 
formation of alkali carbonates which give a pink color with 
phenolphthalein. The standardization should be repeated 
until consecutive results are obtained which check within 0.2 
per cent, of each other. 

Determination. — Remove the cap from the tube in the stop- 
per of the 'bottle, insert the tube-tip of the burette so that it 
projects into the bottle, and run in rapidly 50 c.c. of barium 
hydroxide from the burette. Replace the cap and spread the 
solution completely over the sides of the bottle while waiting 
three minutes for the burette to drain. In doing this take care 
that none of the solution gets into the cap. Note carefully 
the temperature and barometric pressure. Place the bottle 
on its side and roll or shake it at frequent intervals for forty- 
five minutes, taking care that the whole surface of the bottle 
is moistened with the solution each time. At the end of this 
time thoroughly shake the bottle to mix the solution, re- 
move the cap, and pour the solution into a stoppered bottle of 
hard glass of 40 c.c. capacity, taking care that the solution 
shall come in contact with the air as little as possible. Under 
these conditions a full, well-stoppered bottle may safely stand 
for days before titration. For the titration, measure out with 
a pipette 25 c.c. of the clear liquid into a 75-c.c. flask and 
titrate it with the sulphuric acid as in the standardization. 
The difference between the number of cubic centimeters of 
standard acid required to neutralize the total barium hy- 



air: analytical methods. 31 

droxide before and after absorption gives the number of 
milligrams of dry carbon dioxide in the sample tested. The 
results may be expressed in parts per 10,000, by volume, 
under standard conditions (o° and 760 mm.), saturated with 
moisture (Method 1) or dry (Method 2). Tables for this 
purpose will be found in Appendix A.* 

Example. — Data: Standardization, 1 c.c. Ba (0H) 2 = 
1.020 c.c. H 2 S0 4 ; volume of bottle = 8490 c.c; Ba(OH) 2 
used = 49-9 c.c. ; H 2 S0 4 used = 21.1 c.c. ; temperature and 
pressure = 21 and 766 mm. 

Before absorption 

49.9 c.c. Ba(OH) 2 = 49.9 X 1.020 = 50.90 c.c. H 2 S0 4 . 
After absorption 

49.9 c.c. Ba(OH) 2 = 4^2. x 21. 1 =42.12 c.c. H 2 S0 4 . 

.". 8440.1(8490 — 49.9) c.c. air contain 50.90 — 42.12 = 

8.78 mg. C0 2 . 

Method 1. — 1 c.c. C0 2 saturated with moisture at 21° and 

766 mm. weighs 1.79624 mg. (Table II, Appendix A). 

8 78 
.-. 8.78 mg. = — -^ — =4.887 c.c. C0 2 saturated with 

moisture. 

xx r • 1 4.887 

Hence in 10,000 c.c. of air there are -^ — X 10,000 = 

8440. 1 

5.79 parts C0 2 . 

Method 2. — In this method the volume of air is reduced 
to standard conditions of temperature and pressure, under 
which conditions the weight of a cubic centimeter of dry C0 2 
is a constant quantity. 

* Dietrich's Table, the one in general use, is not absolutely correct, the 
weight of a cubic centimeter of carbon dioxide at o° C. and 760 mm. being 
somewhat different from that given at present by the best authorities, but 
it is sufficiently close for any but the most exacting work. 



32 AIR, WATER, AND FOOD. 

Thus v' = v\i + o.oo366(/'— /°)]. v' = 8440.1, t'=2i° r 
t° =zQ°\ hence v = 7&Z7.7 c.c. 

Also, v : v"=H":H, or 7837.7 :*= 760: (766— 18.5)* 
(18.5 = tension aqueous vapor at 21 .) 

Then v" = 7709 c.c. = volume of air at o° and 760 mm. 

I c.c. C0 2 at o° and 760 mm. weighs 1.9643 mg. 

8.78 „ ^^ 4.469 

4.469 c.c. CO2. X 10,000= 5.79 parts 



1.9643 " * 7709 

C0 2 per 10,000. 

Two samples are to be taken, closely following the notes, 
and the results calculated by both methods before collecting 
more samples. Then some one room may be taken and the 
quality of the air determined for the different hours of the 
day, or a comparison of different rooms may be made, or a 
building may be tested as a whole. All data and results ob- 
tained should be arranged in tabular form on a separate page 
of the note-book. 

Notes. — This method of collecting the air in a large bottle 
possesses a decided advantage over the method of slowly 
drawing the air through barium hydroxide contained in a long 
tube, in that a sample represents the condition of the air at 
a given time and not its average condition for a period of an 
hour or so. 

In collecting samples, care must be taken to avoid cur- 
rents of air or the close proximity of people. Duplicate 
samples can be obtained only in empty or nearly empty 
rooms. Even two sides of the same room will probably 
show differences, but two samples taken carefully side by 
side ought to agree within 0.05 part per 10,000. 

The chief source of error lies in the contamination of the 
samples or of the solutions by air from the lungs, the exhaled 
breath containing on an average from 50 to 100 times as 
much carbon dioxide as the air under examination. It is 



air: analytical methods. 33 

hardly possible to exercise too much caution in collecting- 
the samples and in carrying out the analytical procedure. 

All rubber stoppers which are used should first be boiled 
in dilute caustic soda, then in a dilute solution of potassium 
bichromate and sulphuric acid and thoroughly washed. 

Popular Tests. — In addition to the standard method for 
determining carbon dioxide just described, there are also cer- 
tain so-called " popular methods " which can often be used 
with advantage. These methods do not give so accurate re- 
sults as those obtained by the standard method, but on the 
other hand the apparatus required is much simpler and more 
compact, can be more easily carried from one place to an- 
other, and if used carefully and intelligently will give fairly 
good results. Several of these simple tests will be described 
in detail. 

(1) Method of Cohen and Appleyard.* — Principle. — 
This method is based upon the fact that if a dilute solution 
of lime-water, slightly colored with phenolphthalein, is 
brought in contact with a sample of air containing more than 
enough carbon dioxide to combine with all the lime present, 
the solution will be gradually decolorized, the length of time 
required depending upon the amount of carbon dioxide 
present. That is, the quantity of lime-water and the volume 
of air remaining the same in each case, the rate of decoloriza- 
tion will vary inversely with the amount of carbon dioxide. 
The method is scientific in principle because it recognizes the 
fact that the absorption of carbon dioxide by dilute alkali 
solutions is a time-reaction. 

Directions. — Collect several samples of air in white, glass- 
stoppered bottles of one liter capacity, either by exhausting 
the air from the bottle with a pair of bellows or by com- 
pletely filling the bottle with water and then emptying it at 

* Chem. News, JO (7S94), in. 



34 AIR, WATER, AND FOOD. 

the point where the sample is to be taken. Run in quickly 
from the burette 10 c.c. of the standard lime-water (see Re- 
agents, p. 204), replace the stopper and note the time. Shake 
the bottle vigorously with both hands until the pink color 
disappears. Note the time required, and ascertain the cor- 
responding amount of carbon dioxide from the following 
table. 

TABLE. 

Time in Minutes to nrs ._,., Time in Minutes to rn . _,„ . 

Decolorize the Solution. C0 * P er I0 ' 000 - Decolorize the Solution. CO a per IO '° 00 - 

Ii 16.0 3£ 7.0 

i£ 13-8 4 5-3 

l| 12.8 4i 5.1 

2 12.0 5 4.6 

2i 11. 5 5i 4-4 

2| 8.6 6i 4.2 

3i 7.7 7| 3.5 

Modified Cohen Method. — If all the tests of air by this 
method are to be made in the laboratory, it will be 
found best to keep the standard solution in a bottle carefully 
protected from the air, and to draw it off from a burette as 
wanted for each test. In order to make the apparatus more 
portable and convenient for a number of tests at a distance 
from the laboratory, the following modification of the method 
is used, and has been found to give excellent resu 1 ts. The 
10 c.c. portions of the standard lime-water are measured into 
thin glass vials which are tightly closed with rubber stop- 
pers. A number of these vials can be filled at once, since the 
solution will keep its strength for a long time if the vials are 
clean and the stoppers have been boiled with potash and 
bichromate as previously directed. In order to avoid get- 
ting traces of acid on the outside of the filled vials through 
handling, it is best to rinse them off thoroughly and keep 
them in a beaker under water until wanted for use. The 
samples are collected in the bottles as before, the glass stop- 



air: analytical methods. 35 

per removed for a second, and the vial of lime-water quickly 
dropped in, stopper downward. The bottle is shaken once 
violently to break the vial, and is then shaken with a rotary 
motion until the solution is decolorized. If desired, a bottle 
of half the size, and smaller vials holding only five cubic 
centimeters of solution, may be used. 

Note. — Much of the difficulty experienced in the use of 
these simpler methods arises from the lack of defmiteness in 
the composition of "a saturated solution of lime-water" which 
is generally recommended for use in making up the test solu- 
tion. The amount of lime that water will take up varies 
considerably with the way in which the solution is made; for 
example, whether the water is simply shaken up with a cer- 
tain quantity of lime, or whether the solution, once saturated, 
is kept standing over an excess of lime. For this reason it 
is much better to have the strength of the lime solution 
definitely fixed by some method of titration. 

(2) Method of Dr. G. W. Fitz — Principle.— In this 
method the volume of air that must be brought in contact 
with a definite quantity of lime-water, in order to neutralize 
all of the lime, is taken as a measure of the amount of carbon 
dioxide in the air. The quantity of lime-water and the time 
of reaction remaining constant, the amount of carbon diox- 
ide will vary inversely as the volume of air required. In this 
laboratory the same solution is used for this method that is 
used in the Cohen method. The apparatus consists of a 
graduated tube or " shaker," of about thirty cubic centimeters 
capacity, and a number of homoeopathic vials, each containing 
ten cubic centimeters of standard " lime-water." 

Directions.— Be sure that the inner tube of the shaker 
slides easily within the outer one, then remove the inner 
tube and pour into the large tube the contents of one of the 
vials. Introduce the inner tube and press it to the bottom 



36 AIR, WATER, AND FOOD. 

of the larger, then withdraw it to the " T " mark, the bottom 
of the inner tube serving as the index. Close the mouth of 
the small tube with the finger and shake the instrument vig- 
orously for thirty seconds. The volume of air thus brought 
in contact with the solution is 30 cubic centimeters, as there 
are 25 cubic centimeters of air above the solution when the 
inner tube is forced to the bottom of the larger. Then re- 
move the finger closing the small end, press the inner tube to 
the bottom of the larger and draw it up again to the 20-c.c. 
mark, thus admitting 20 cubic centimeters of fresh air. 
Shake the apparatus again for thirty seconds. The total 
volume of air now used is 30 + 20 c.c. = 50 c.c. Repeat the 
operation until the color of the solution is discharged. The 
first trial made will probably give the approximate amount 
of carbon dioxide, and subsequent tests with the other vials 
will aid in giving the correct result. After determining the 
volume of air which is required to decolorize the solution 
reference is made to the table given below. 









TABLE. 






Air in c.c. 


used. 


co a 


per 10,000. Air in c.c. used. 


C0 a 


per 10,000. 


30 






28 91 




9 Bad 


36 






22 103 




8 


46 






18 Very bad 117 




7 


58 






14 138 




6 


69 






12 165 




5 Good 


82 






10 207 




4 



Notes. — The stoppers and vials should be washed and 
dried after use and kept separate, and the parts of the shaker 
should be kept separate. 

In using the shaker see that the fingers are clean, or close 
the mouth of the shaker with a rubber stopper instead of the 
finger; also take care to avoid loss of liquid upon the addition 
of fresh air. The same objection applies to this method as 
to the tube method of Pettenkofer, namely, that the air taken 



air: analytical methods. 37 

is an average sample extending over some time and does not 
show its condition at any one time. New stoppers should 
be boiled in dilute caustic soda and then in bichromate solu- 
tion before being used. 

(3) Wolpert's Method. — Principle. — When air contain- 
ing carbon dioxide is passed through lime-water the solution 
gradually becomes turbid from the formation of calcium car- 
bonate, and the richer the air is in carbon dioxide the less 
will be the volume of air required to produce a definite degree 
of turbidity. This is the principle on which this simple 
method is based. 

Directions. — A small test-tube provided with a black ref- 
erence-mark on the bottom is filled to a definite height with 
" saturated " lime-water. The air is collected in a small rub- 
ber bulb and slowly forced through the solution, the 
operation being repeated until the reference-mark can no 
longer be seen through the turbid solution. The instrument 
is first calibrated by observing the volume of air required to 
produce turbidity out of doors or in some room where the 
percentage of carbon dioxide is known, after which it affords 
a ready means for comparative tests in cases where the air 
contains 20 parts or more. For testing modern systems of 
ventilation, where the amount is usually less than 8 parts, it 
does not give reliable results. The difficulties in the use of 
this method are the same as those noted under the Fitz meth- 
od, with the increased error due to the solubility of calcium 
carbonate in solutions of carbon dioxide. 

(4) Wolpert's "Luftpriifer" (Air-tester). — This is an- 
other simple instrument for testing the purity of the air. 
Its action is based upon the well-known fact that the alkali 
carbonates give a pink color with phenolphthalein, while the 
bicarbonates do not. By means of a capillary siphon a one 
per cent, solution of sodium carbonate colored with phe- 



38 AIR, WATER, AND FOOD. 

nolphthalein is allowed to drop at regular intervals upon a 
cord suspended vertically. As the solution flows down the 
string it absorbs carbon dioxide from the air, converting the 
sodium carbonate into the bicarbonate, so that the lower part 
of the cord will be white, while the upper part is pink. The 
height of the dividing line indicates on a scale the amount of 
carbon dioxide in the air. The chief value of this instru- 
ment lies in the fact that it acts continuously, one filling 
being enough to last for ten days, and can be consulted at 
any time to learn the condition of the air, just as a ther- 
mometer is used to indicate the temperature. In practice 
the usefulness of the apparatus has not been fully realized on 
account of the dryness of the air in ordinary rooms, which, 
interferes with the continuous flow of liquid down the cord. 

Carbon Monoxide. — The detection and estimation of 
carbon monoxide in the very minute quantities in which it is 
found in the air of ordinary rooms is a problem of consider- 
able difficulty. 

Detection. — Probably the most convenient test for detect- 
ing small quantities is the blood test. Dilute a large drop 
of human blood, freshly drawn by pricking the finger, to 10 
c.c. with water. Divide the solution into two equal portions, 
and shake one portion gently for ten minutes in a bottle con- 
taining about ioo c.c. of the air to be tested. Compare the 
tints of the two portions by holding them against a well- 
lighted white surface. The presence of carbon monoxide is 
indicated by the appearance of a pink tint in the blood which 
has been shaken with air. One part in 10,000 can be de- 
tected in this way.* The delicacy of the test can be increased 
by examining the blood, after shaking with the air, with 
a spectroscope. By collecting the sample in an 8-liter bottle 

* Clowes: " Detection and Estimation of Inflammable Gas and Vapor 
in the Air," p. 138. 



air: analytical methods. 39 

and examining it in this way o.oi part in 10,000 may be de- 
tected. 

Determination.* — Principle. — Oxidation of the carbon 
monoxide to carbon dioxide by iodine pentoxide, iodine 
being liberated according to the following equation: 

I 2 5 +5CO= I 2 + 5C0 2 . 

N 

The iodine is titrated with sodium thiosulphate. 

1000 r 

Directions. — Place 25 grams of iodine pentoxide, free from 

iodine, in a small U tube which is suspended in an oil-bath 

and connected with a small absorption-bulb containing 0.5 

gram of potassium iodide dissolved in 5 c.c. of water. Heat 

the oil-bath to 150 C, and pass the air, previously drawn 

through U tubes, — one containing sulphuric acid and the 

other solid potassium hydroxide, — through the apparatus at 

the rate of a liter in two hours. Titrate the liberated iodine 

N 

bv sodium thiosulphate and starch. 

J 1000 r 

Notes. — The temperature and barometric pressure should 
be noted and all volumes reduced to o° C. and 760 mm. pres- 
sure. 

Using 1000 c.c. of air, it is possible to determine in this 
way 0.25 part per 10,000, by volume, of carbon monoxide. 

The use of tubes containing sulphuric acid and potassium 
hydroxide is to free the air from unsaturated hydrocarbons, 
hydrogen sulphide, sulphur dioxide, and similar reducing 
gases. 

Nitrites. — The determination of the amount of nitrites 
or nitrous acid in the air can be readily made as follows: 
Collect a sample of the air in a calibrated eight-liter bottle, 
as in the determination of carbon dioxide. Add 100 c.c. of 

* Kinnicutt and Sanford: Jour. Am. Chem. Soc, 22 (igoo), 14, 



40 AIR, WATER, AND FOOD. 

N 
approximately — sodium hydroxide solution. (This should 

be free from nitrites and is best made by dissolving metallic 
sodium in redistilled water.) Shake the bottle occasionally 
and let it stand for about twenty-four hours. Take out 50 
c.c. of the solution and determine the amount of nitrites as 
directed on page 94. 

Micro-organisms. — For the quantitative determination 
of the number and distribution of the micro-organisms in air, 
the method employed by Tucker * in the examination of the 
air of the Boston City Hospital answers very well. The 
apparatus used consists essentially of three parts: (1) a 
special glass tube called the aerobioscopc, in which is placed 
the filtering material; (2) a stout copper cylinder of about 
sixteen liters capacity, fitted with a vacuum-gauge; (3) an 
air-pump. The filtering medium which is used to retain the 
micro-organisms is a narrow column of sterilized granulated 
sugar about four inches long. 

In using the apparatus, the required amount of air is first 
drawn from the cylinder by means of the air-pump. A 
sterilized aerobioscope is then attached to the cylinder and the 
air is slowly drawn through it, leaving its germs in the sugar- 
filter. After the air has been drawn through, the aerobioscope 
is taken to the culture-room and the sugar dissolved in 
melted sterilized nutrient gelatine. The gelatine is con- 
gealed in an even film on the inside of the tube, where, after 
four or five days, the colonies will develop, and can be 
counted by the aid of squares engraved upon the glass. 

This method possesses several peculiar advantages. The 
use of a vacuous cylinder allows a known volume of air to be 
readily aspirated, and the rate of flow through the filter is 
easily controlled. Another great advantage is the use of a 

* Report State Board of Health, Mass., 1889, 161. 



air: analytical methods. 41 

soluble filter (sterilized granulated sugar), since insoluble 
substances seriously interfere with the counting. Further- 
more, the removal or transference of the filter and its germs 
is avoided. The apparatus is portable, and the method, as 
compared with others, is exceedingly rapid of execution. 

Organic Matter. — In regard to the presence of organic 
matter in the air there is at present considerable variance of 
opinion. While some investigators have obtained results 
which indicate the presence of such organic matter, it has 
been found also that the amount which is obtained is very 
much less when the dust of the air is first removed by filtra- 
tion. The quantity of organic matter is therefore closely re- 
lated to the amount of dust, and there is strong evidence that 
this dust in the air is the source of the greater part, if not all, 
of the organic matter, unless there are present persons with 
decayed teeth, diseased lungs, etc. 

The methods of determination that are in general use 
may be divided into two groups. In the first group are 
those methods in which the organic matter is converted into 
ammonia and determined by Nessler's reagent. In the sec- 
ond group the organic matter is oxidized by boiling with 
dilute potassium permanganate, the excess being titrated 
with oxalic acid. No one method gives results which are 
wholly satisfactory, the chief difficulties being to secure an 
absorbing material which shall itself be free from organic 
matter, and to avoid the introduction of minute particles of 
organic matter or dust during the analytical process. 

Remsen * and Bergey f recommend the use of freshly 
ignited granular pumice-stone contained in a narrow glass 
absorption-tube. After aspirating a known volume of air, 
the pumice-stone is transferred to a flask, the ammonia dis- 

* National Bd. Health Bulletin, I, 233; II, 517. 

f Mis. Coll of Smithsonian Institution, No. 1037 (iS<p6). 






42 AIR, WATER, AND FOOD. 

tilled off from alkaline permanganate and estimated by Ness- 
ler's reagent. Experience with the method in this labora- 
tory has shown that it is practically impossible to prepare the 
pumice-stone so that it shall be absolutely free from organic 
matter, and that the mere act of transference of the absorb- 
ing material resulted in a considerable error. Miss Talbot * 
found, furthermore, that all of the organic matter is not con- 
verted into ammonia by a single distillation, but that a second 
and third redistillation of the distillates uniformly gave 
higher results. She found it preferable to draw the air 
directly through the boiling permanganate, having the ap- 
paratus so arranged that the condensed steam was returned 
to the flask. In this way the particles of organic matter were 
returned again and again to be acted upon by the perman- 
ganate. 

Experience with all these methods is well summed up by 
Professor Remsen when he says: "It would be useless to 
have examinations of air made by any but the most careful 
workers. It would be time thrown away to have such an- 
alyses made by the average practical chemist." 

Dust and Soot — The dust in the air may be estimated by 
drawing a measured volume through tubes packed with cot- 
ton and noting the increase in weight. Soot may be deter- 
mined by drawing the air through combustion-tubing partly 
filled with ignited asbestos, and then determining the carbon 
by the ordinary methods of combustion. 

* Tech Quart., I {1887), 29. 



■^M 



CHAPTER V. 

WATER : ITS SOURCE, PROPERTIES, AND RELATION TO LIFE 

AND HEALTH. 

{From the Householder' s Standpoint.) 

The metabolism which produces human energy is depen- 
dent upon the presence of water in the tissues. This water 
is derived in part from food which, as eaten, contains from 
30 to 95 per cent.; in part from boiled water, as in tea and 
coffee; or raw from well or city tap. The total daily supply 
per person for this purpose from all sources is five or six 
pints. 

Water is also necessary to all forms of vegetable and 
animal life, even the lowest types, including those inim'cal 
to human health. Man has always used water as his beast of 
burden: to carry ships to the ocean, to turn mill-wheels, to 
generate electrical power. He has also forced it to be his 
scavenger, carrying the refuse of his activities out of his sight. 
Unless compelled by legal restrictions, he has given little 
thought to the effect on his neighbor of this treatment of 
their common property. 

In common law, water is held to be a gift of nature to 

man for use by all, and therefore not to be diverted from its 

natural channels for the pleasure or profit of any one to the 

exclusion of the rest. Neither has one the right to return 

to the channel water unfit for the use of his neighbor farther 

down the stream. That is, there is no private ownership in 

43 



44 AIR, WATER, AND FOOD. 

surface-waters flowing in natural channels. But this inter- 
pretation of eminent jurists has not always been strictly fol- 
lowed. Many cases have been decided, especially since the 
rapid growth of large cities, in direct contradiction to this 
law. As population increases, cities need to go farther and 
farther into the country for their water-supply, and they 
often take from the few settlers found there the right to the 
water which passes their doors, for the benefit of far-away 
thousands. 

The law in regard to that portion which never enters, or 
which escapes from visible channels, is less clear. It is usu- 
ally held that this water goes with the soil, and that rights 
to it may be bought and sold: that wells may be driven and 
drains dug, even if a neighbor's supply is cut off; but it is 
always maintained that no man has a right to place any sub- 
stances on or in the ground which shall render his neighbor's 
well unfit for use. 

The changes in conditions of life have rendered impera- 
tive a careful study of the ways and means of practically com- 
plying with the law's demand without a serious restraint upon 
the progress of civilization. 

The daily quantity required for each person has increased 
from the two to four gallons drawn by bucket from the farm- 
house well to thirty or forty gallons taken from the town sup- 
ply by the turning of a faucet, and in cities where much is used 
for manufacturing purposes, for running elevators and 
motors, the daily amount may reach ioo gallons per inhabi- 
tant. This constantly increasing use of water for other than 
cleansing purposes has enormously increased the difficulty 
of securing clean water for domestic use. Not only is a 
larger quantity of polluting material deposited in the water, 
but it is carried farther from its source by the dilution. 
This fact, as well as the demand for higher standards of 



water: source, properties, and relation to life. 45 

purity, has made the abandonment of private water-supplies 
a necessity, and has demanded from municipalities the best 
scientific knowledge and the most careful supervision of the 
quality of the public supply. 

A city or town is under as strict obligation to furnish a 
safe supply of water as it is to provide safe roads. To this 
end, the proper construction and maintenance of reservoirs 
and a sufficient police surveillance of the watershed is as im- 
portant as abundance of supply. 

Education of the people at large is still necessary, not 
only that those who depend in whole or in part upon springs 
and wells may know how to protect themselves, but also that 
the necessary cost of the larger public (municipal) supply 
may be cheerfully paid for by the citizens. 

Leaving out of the present discussion such considerations 
as belong only to the engineer and specialist, the problem of 
potable water will be treated in this chapter from the point 
of view of the intelligent citizen and educated individual who 
cannot afford to remain ignorant of so important a factor in 
the general welfare. The reason why this education is needed 
lies in the fact that primitive habits of thought, influencing 
action in every-day life, survive long after the race has passed 
beyond the original conditions. In no respect is this more 
true than in regard to water. 

The ideal drinking-water of most persons is the clear, 
colorless, sparkling water of a spring, refreshing in its cool- 
ness and satisfying the aesthetic sense by its suggestion of 
purity. So strong a hold has this ideal that it is most diffi- 
cult to convince the average person that any water which has 
these characteristics can be other than wholesome and, con- 
versely, that water lacking in any of these qualities is suitable 
for human consumption. Early man drank clear cool water 



46 AIR, WATER, AND FOOD. 

wherever he found it. If there was not a spring at hand, he 
scooped out a hole in the sand. Pioneer settlers dug the 
well as near the kitchen door or the barnyard as they could 
find water, with a blind faith in the protecting power of 
mother earth, not wholly misplaced so long as the require- 
ments of the household did not exceed two or three gallons 
per person daily, and so long as the nearest neighbor was 
half a mile away. So persistent is this confidence in nature 
that in the light of this day a majority of intelligent people, 
even, will quaff at a roadside well or drink freely at a country- 
hotel or go to live in a city without ever taking thought for 
the quality of the water. Water is water, and he who pauses 
with his glass half-way and asks whence comes the supply is 
scouted as a weak-minded crank. So, too, when town au- 
thorities have spared no pains or expense to secure a safe 
supply from a distant lake, and have guarded it by all means 
known to science, the primitive habit of thought requiring 
colorless water of an even coolness of temperature leads 
those who can afford it to purchase " spring ''-water in jugs 
and bottles, with the blind faith of the savage that what comes 
out of the ground must be good. 

Fundamental race-habits are taken advantage of by the 
dealer in spring-waters as well as by the vendor of patent 
medicines — the missionary has no chance against him. 
From the schools and colleges there should, however, 
be sent out a generation of more intelligent persons who, 
learning to weigh evidence, will not take chances and 
will help to develop a public opinion on sanitary matters, 
especially in regard to water-supplies. For not until 
there is an intelligent public can the present reckless use of 
water and ground be stopped. While not every man may 
be a chemist, he can have that modicum of knowledge which 
will enable him to understand the need of chemical tests of 



water: source, properties, and relation to life. 47 

water and to distinguish between the work of the expert and 
the amateur. 

However safe this ideal of clear, colorless water may have 
been in early times, it must now be relegated, with the un- 
barred door and unwatched treasure, to the mountain fast- 
nesses. As the country becomes settled, appearance and 
taste are no longer sufficient guides; therefore scientific tests 
must be applied and the results interpreted by trained ob- 
servers to whom the individual subordinates his private 
judgment. 

The ideal water should be above suspicion, for if it has 
once been contaminated, who can tell how soon it will find 
bad company again? Not the analyst in his laboratory. In 
fact, the laboratory verdict is worth very little without a 
knowledge of outside conditions and without a keen detec- 
tive insight which scents out the most unlikely causes. 
Nevertheless the evidence given by analytical results is 
needed to procure conviction. 

Although " pure " water is found only in the laboratory, 
" safe " water, that which is reasonably free from objection- 
able substances, mineral and organic, may be obtained with 
sufficient care and knowledge. 

A clear understanding of the problem requires a close 
study of the circulation of water on the earth. Let us trace 
the course of water from sky to ocean, in view of its availa- 
bility for domestic use, and note the dangerous properties it 
may acquire, considering also the changes in condition which 
it may undergo in its course from mountain to sea. 

Water-vapor rising from sea and land is condensed in the 
upper air, then falls to the earth, absorbing, as it does so, 
ammonia, carbon dioxide, sulphur oxides, and other soluble 
gases, if present, and washing the air free from dust-particles, 
mineral and organic. 



48 AIR, WATER, AND FOOD. 

This meteoric water (rain or snow), although nearly free 
from dissolved mineral substances, is therefore by no means 
pure. Furthermore, rain falling on insoluble rocks, bare or 
lichen-covered, or on loose, sandy soils, washes them also, 
giving up to the vegetation the ammonia and taking in re- 
turn carbon dioxide and dissolved albuminoid ammonia. 

Water thus enriched has increased solvent power on cer- 
tain rocks and soils. This rain-water soon forms rivulets 
which, passing down from the highlands into the forest, spread 
over the moss-covered area, soaking the leaves and peaty soil 
and extracting organic substances. Mountain brooks, as well 
as lowland streams, draining a region free from limestone, are 
thus colored brownish-yellow and furnish " meadow-tea/' as 
Thoreau happily named it. As the stream flows on it re- 
ceives contributions of many kinds — the overflow of springs, 
the under-drainage from cultivated fields, the surface-wash 
from pasture and meadow. Scavengers are, however, con- 
stantly at work. Brought as dust by the ever-passing air- 
currents, seeds of tiny plants freely sprout in the water and 
grow rapidly whenever a quiet pool or lake gives oppor- 
tunity. The products of organic decay and the ammonia of 
the rain may be thus removed and the water pass on to the 
reservoir clear and soft and as nearly pure as nature furnishes. 
It is, however, becoming rare to find even a mountain stream 
or forest brook which has not been subjected to modification 
by human agencies. Three kinds of contamination may take 
place. First: A farmhouse high up on the hillside lays trib- 
ute for drinking purposes upon that water finding its way 
beneath the sand which appears in the form of a spring. The 
overflow is made into a duck-pond, or passes through the 
watering-trough by the roadside before it joins other water 
tumbling over the rocks as a rapid stream. The brook thus 
grown larger widens out a little below the farmhouse into a 



water: source, properties, and relation to life. 49 

shallow pool, in which one or two cows frequently seek com- 
fort. The water has become rich in organic matter and sup- 
ports a thick growth of tiny plants; the stones, even, may be 
coated with green slime. This vegetation serves as a warning 
to the hunter and the woodsman, who wisely drink only of 
water from clear pools with bottom of shining sand. The 
heavy material stirred up by the cattle soon settles, leaving 
the water in the stream below clear, although probably a little 
yellow in color. It still tastes well and looks all right, and 
may be used by human beings with probable impunity. 

Second: The little stream next passes other farm build- 
ings, where the privy is put over it to save the trouble of 
cleaning, or, even if not so close, is placed in such a way as to 
allow of a possible wash into it, especially in times of sudden 
rain. 

A case of typhoid fever develops at this farm. No pre- 
caution is taken to disinfect the discharges, and a portion of 
the dangerous material is carried into and along with the 
water. Some two or three miles below, another farmhouse, 
having no spring, uses this same little stream for its supply, 
perhaps damming it up into a little pond or pumping it into 
a tank. All unconscious of what has happened above, or 
ignorant of consequences, this water with a history is freely 
used, and perhaps the whole family come down with the dis- 
ease, perhaps only the delicate one may have it. It may be 
that they will all escape, owing to the fact that they were 
particularly robust, or that they drank no water raw, or that 
the conditions on the stream have been favorable to purifica- 
tion of the water by storage and consequent growth of the 
green plants, which are our friends in such cases; but if the 
water were pumped into a covered tank and used soon after, 
the chances are nine to one that some deleterious results 
followed. r 



50 AIR, WATER, AND FOOD. 

Third: A part of the water sinks through the sand, and by 
this filtration becomes freed from all suspended matter and 
consequently from the germs of disease, if present. In its 
course if it is intercepted and collected in a shallow well it 
may again be of great organic purity and free from danger, 
but it will surely bear the telltale marks of its progress in 
the increase of chlorine and solids which will have escaped 
all the agents of purification, and in the nitrates, the result of 
the process. 

It will be noticed that it is only after contamination with 
the " waste of human life " that danger comes to other human 
beings and that many circumstances modify that danger. 
The chances are about equal to those of fire; and as most 
householders think it worth while to insure against possible 
fire, so they should hold the chemist's certificate as a sort of 
water insurance; but since the fire policy does not protect 
from carelessness, the knowledge that the water-supply is 
once good does not absolve the householder or the citizen 
from the greatest care in protecting his premises. Duty to 
his neighbor should lead him to see that this coin of the 
world is passed on in as good condition as possible, and he 
should at least give notice of danger when he knows that it 
exists. 

But this general movement of water on and near the sur- 
face is not all the story. From 25 to 40 per cent, of the 
annual rainfall, in temperate regions, soaks at once into the 
ground, and passing downward through the soil to hard-pan, 
to clayey or impervious layers, or to rock surface, thence 
through crevices, broken joints, or glacial drift-deposits to 
the water-table, flows along the slope for many miles, until 
it finds its way again to the surface, either from the bottom 
of a lake, the bed of a river, the side of a hill, supplying wells 
or appearing as a spring free from all organic and suspended 



water: source, properties, and relation to life. 51 

matter but often rich in gases. In any one of these courses 
it may be intercepted by man and caught or pumped for his 
use. Such water may never have been far from the surface; 
it may have been used and returned to the ground many 
times; it may have appeared as surface-water and again dis- 
appeared to great depths. It has been estimated that water 
moves in the ground at rates varying from 0.2 to 20 feet per 
day. This long contact with rocks will, of course, bring min- 
eral substances into solution which may be precipitated as 
new rocks are reached or other streams encountered, so that 
the same gallon of water may have had many stages in its 
course and may have held many different substances in solu- 
tion. An example of how much can be so held is found in 
the waters of the alkali belt (page 199). 

It is no wonder that so active a solvent as water should 
take with it much substance whenever it remains long in con- 
tact with soil or rock, for it may be many months before that 
which has once sunk out of sight again appears. In fact, great 
rivers are supposed to flow into the sea from under the sur- 
face. 

Then, too, the acquisition of dissolved gases favors the 
solution of many substances; for instance, water carrying 
carbon dioxide dissolves limestone as well as lead and cop- 
per, and when at low temperature and containing ammo- 
nium carbonate water may dissolve ferric iron. 

Water carrying organic acids dissolves among other sub- 
stances iron compounds which may or may not be in the 
ferrous condition, and therefore may or may not be precipi- 
tated on coming to the surface. And as we have seen that 
the ground below a certain level is permeated with moving 
water, whatever is buried in the earth is likewise liable to enter 
the watercourses in one form or another. 

An understanding of this movement of water under- 



52 AIR, WATER, AND FOOD. 

ground, with the accompanying changes in its character,, 
cannot be too strongly insisted upon, for the lack of com- 
prehension of it is at the root of most of the troubles from 
well-waters. For example, the leaching cesspool, the primi- 
tive " septic tank," delivers its more or less filtered water rich 
in nitrogen compounds into the general circulation at a 
depth below the most efficient action of the nitrifying or- 
ganisms, hence it may permit the passage of organisms of 
putrefaction into underground streams or into the w ell, when 
access is direct. Even when filtration is perfect, the products 
of decay are yet carried with it and so tell the story of the 
past. The difficulty is to determine the state of the filter 
which may be on a neighbor's land many hundred feet away,, 
and to be sure that its action is uniform. Experience with 
artificial filters shows how difficult it is to maintain efficiency 
with rapid use; hence heavy rains or wet years may cause a 
state of danger not ordinarily existing. 

The relation of water to human health must be consid- 
ered chiefly in the light of the changes which go on in the 
substances held suspended or dissolved in it, and the effect 
of these changes on the wholesomeness of the water. The 
suspended matter may be either inert, as clay or sand; dead 
vegetable, as fragments of plants; living vegetable, as plants 
floating on the surface, diatoms, desmids, algae, etc.; dead or 
living animal, as infusoria, small crustaceans, etc. 

Wherever these occur there are found the lower orders 
of vegetable organisms, fungi, moulds, bacteria, ready to do 
the necessary work of decomposition preparatory to solu- 
tion. The mere presence of these forms of living matter 
does not of itself mean danger to those using the water, but 
among these may be found pathogenic organisms which are, 
at present, considered as liable to cause disease. Such mi- 
crobes do not find in water a congenial habitat, and, fortu- 



water: source, properties, and relation to life. 53 

nately, do not thrive on the vegetable diet and in the cool tem- 
perature of natural waters, hence the other organisms soon 
overpower them; danger decreases not only in proportion to 
distance, time, and dilution, but also, probably, to the abun- 
dance of other vegetable life. Under favorable circum- 
stances the danger is, however, a very real one. 

The presence of certain living plants may, moreover, give 
rise to unpleasant, if not dangerous, tastes and odors, due to 
the presence of extremely pungent oils or other aromatic 
substances formed in the process of growth. When these 
plants are decaying putrefactive odors are also present, some- 
times rendering the water too offensive for use. These or- 
ganisms are described in Whipple's " Microscopy of Drink- 
ing-water," and in Chapter VII a short list of those which 
give characteristic odors will be found. 

The presence of much decaying vegetable matter in 
drinking-water is to be avoided, since it is not known what 
effect it may have upon the general health of the individual, 
rendering him perhaps more susceptible to disease. 

Food-supply is a necessary condition for life, and there 
cannot be abundant growth in a water without a correspond- 
ingly large amount of dissolved substances furnishing the food 
for this living fauna and flora. As has been stated, water 
usually carries considerable mineral substance and is often 
supplied with organic and gaseous compounds, while nitro- 
gen is furnished from many sources, most abundantly from 
sewage, so that it is not strange that water-life is so abundant, 
but rather that it is not more so. Most of the difficulties in 
securing a satisfactory water-supply are connected with the 
cycle of nitrogen in its relation to organic life. 

This may be briefly stated as follows: Nitrogen is found 
as an essential constituent of all living matter. When thus 
combined, it is the so-called organic nitrogen, and is found 



54 AIR, WATER, AND FOOD. 

in undecomposed vegetable or animal substances. As soon as 
dead, these substances may become food for micro-organisms 
and the nitrogen then appears in a form from which it can be 
obtained as ammonia; for instance, from decaying beans, from 
putrefying broth, and from fresh sewage. This process takes 
place with or without much air and may be accompanied by 
very bad odors. As soon, however, as the nitrogen has passed 
from the insoluble organic form into the soluble compounds 
from which ammonia is obtained, then, if oxygen is present, 
and only then, another set of micro-organisms take up the 
work and nitrites appear; when still another set have done 
their work the nitrogen is found only in combination as ni- 
trates, fully oxidized and mineralized, no longer organic or 
capable of sustaining the life of the lower forms of vegetation, 
but, on the other hand, the most valuable food for chlorophyll- 
bearing plants which convert nitrates again into organic 
nitrogen. This cycle may be arrested or broken at certain 
stages. If the soluble ammonia compounds are set free out 
of contact with air or below the layers of soil containing the 
nitrifying organisms, they may remain indefinitely un- 
changed. If nitrates have been carried below the reach of 
the roots of the chlorophyll-bearing plants, or if they are con- 
fined in a space deficient in oxygen, then an access of decom- 
posable organic matter with micro-organisms will cause a 
reduction of the nitrates to nitrites and free nitrogen, through 
the action of these lower plants which, in the absence of 
air, take the little oxygen they need from mineral com- 
pounds. 

These micro-organisms are not the only ones at work, 
however. In any sudden prominence of one factor others 
are apt to be overlooked; thus in the present case the in- 
finitely small has so powerfully affected men's minds that, 
partly because the micro-organisms are beyond their range 



WATER: SOURCE, PROPERTIES, AND RELATION TO LIFE. $$ 

of vision, such forms of life as are evident to the naked eye 
or with low powers of the microscope have been overlooked 
to an extent. 

As agents of putrefaction and of decay the micro-organ- 
isms have their work to do, but the final purification — the 
finishing up of the work — belongs to another order of life. 
The still minute but visible green plants — those which float 
free in water or attach themselves to larger growths — have 
now their part to play. The life-history of these forms has 
been little studied, and the work they do in the actual puri- 
fying of polluted water has been almost overlooked. The 
impression left on reading most books is that when foul mat- 
ter has been dissolved and converted into ammonia, carbon 
dioxide, and nitrates the work is done, but these compounds 
only furnish food for the next class, and these again for in- 
fusoria, tiny crustaceans, etc. 

In some cases these organisms succeed each other with 
great rapidity; in one case the fauna and flora of a given 
pond varied each week of a season, certain rare forms being 
found only once. 

There is needed, almost more than anything else, a con- 
secutive study of the green plants found in water-supplies, 
since by their cultivation greater purity might be attained 
and possibly a way might be found of exterminating the dis- 
agreeable ones. The most unexpected results may follow 
the long study of a single organism, such as has been given 
to Oscillaria prolffica of Jamaica Pond for a period of eleven 
years. Weekly, sometimes daily, observations have been 
made for two or three years.* 

It is organisms of this class which give tastes and odors 
to water, and which, if enough were known concerning them, 

* Trans. A. A. A. S., 1898. 



56 AIR, WATER, AND FOOD. 

would probably give perfectly trustworthy evidence as to the 
past history or source of contamination. 

The two classes of organisms work in opposite directions, 
and so long as food is present for either, life will increase with 
proportional rapidity. This connection of cause and effect 
should be made familiar to the intelligent citizen. When a 
ground-water free from all organic matter but rich in 
nitrates is exposed in an open basin the rich growth of 
chlorophyll-bearing algae follows as a matter of course; later, 
decay sets in and products of decomposition abound, the air 
above being the source of a constant supply of spores of all 
kinds. 

When a house- or barn-drain empties into a small slug- 
gish stream, it soon becomes filled with green plants thriving 
on the ammonia, and it is often possible to trace the source 
of pollution of a large lake by the line of green anabasna 
leading to the insignificant ditch. 

A curious blindness on the part of managers of water- 
works to the movements of water and its action in transport- 
ing material is seen not only in the almost universal proximity 
of cemeteries to reservoirs, but also in the common practice 
of dressing the sloping banks of turf with a heavy coating of 
manure. Even if this was derived from clean stables and 
was not liable to be contaminated with night-soil, the abun- 
dant food for plants which inevitably finds its way into the 
reservoir occasions as fruitful results in the water as on the 
banks, and is undoubtedly the cause of much of the trouble 
in storage basins. 

It is evident, therefore, that a once polluted water cannot 
be said to be purified so long as food for green plants re- 
mains, for the moment the temperature and other conditions 
become favorable growth will begin. The term " purifica- 
tion," taken in a chemical sense, should not be loosely used. 



water: source, properties, and relation to life. 57 

Complete purification can take place only when all traces of 
former impurity, in any form, have been removed. Chemical 
precipitation of sewage leaves the soluble ammonia, and sand 
filtration leaves nitrates to serve for abundant life and sub- 
sequent decay in the streams into which the effluents flow. 
Such effluents are clarified and the organic matter may have 
been mineralized, but. this is not purified water. Only when 
growing plants have removed this food and have themselves 
been removed can the water approach a purified condition. 

The effect of storage of water containing high nitrates 
in open tanks or reservoirs exposed to the collection of dust 
will be that spores of chlorophyll-bearing algae, diatoms, 
desmids, etc., will soon develop and will increase as long^as 
the food (nitrates, mineral matter, etc.) lasts. Only by pro- 
tection from dust and light can such water be kept free 
from unpleasant accumulations of suspended organisms or 
from disagreeable tastes. Unpolluted surface-waters, on the 
other hand, improve on storage, as a general rule, if the basin 
is a clean one. The storage of polluted or clarified water is 
thus forbidden, since not infrequently the first indication of 
the pollution of a surface supply is given by the appearance 
of some member of that richly nitrogenous group of algae 
called cyanophycece, or " blue-greens," from the presence of 
blue or purple coloring matter along with the yellow-green 
chlorophyll. Since this group of plants contains from seven 
to eleven per cent, of nitrogen, while other groups contain 
only one or two, it is evident that, if it is to flourish, more 
nitrogenous food must be supplied. This may be derived 
from fertilized fields, from decay of other vegetable life, as 
well as from the richer source of direct sewage; but, in any 
case, the growth of these plants is a sign of abundant food- 
supply which must be cut off if they are to be starved out, as 
they must be unless they are removed while fresh by strain- 



58 AIR, WATER, AND FOOD. 

ing or skimming, for the odor of their decay is so intolerable 
as to preclude the use of the water. In some cases the odor 
accompanying their growth renders the water quite objec- 
tionable, and neither natural nor artificial filtration is able to 
remove it. 

Either natural or artificial basins may have a collection of 
vegetable matter on the bottom which slowly decomposes 
in summer, and since the bottom water is colder, the resulting 
ammonia remains until the late fall overturn, when it is 
brought to the surface, where it favors the growth of diatoms 
and other cold-water plants. Certain diatoms, as asterio- 
nella, cause disagreeable odors. Such basins show the least 
ammonia in early October and the most in late November. 

In order to make any predictions as to the probable de- 
velopment of this flora and fauna of water, experience and 
at least a year's watching of any given supply are required 
until more is known of the life-history of these forms of life. 
Nothing is more needed to-day than work along these lines. 
When may disagreeable odors and tastes be expected? 
What precaution or measures may be taken in each case to 
prevent them? These are the questions the water-works 
superintendent, equally with the consumer, is asking, for the 
most part vainly as yet. 

As has been stated, surface-waters often carry stable or- 
ganic matter in connection with color, so that while the 
organic nitrogen shows high, no free ammonia or nitrates are 
formed on standing. These weak meadow-teas are now 
largely used for town supplies, and a word as to the source 
of the color may not be amiss. Many carbonaceous sub- 
stances, sugar, for example, when partially broken up become 
caramelized and give a brown solution, the color being due 
to substances richer in carbon; this color is deeper as the 
decomposition is more complete. There is no reason to sup- 



water: source, properties, and relation to life. 59 

pose that such compounds have any deleterious effect on 
health. Indeed, experience has proved that such waters are 
more reliable than many others. 

The chlorine of unpolluted natural waters is derived from 
the sea in past or present times. Waves breaking on a 
rocky shore send finely divided salt-spray high into the air; 
dust-particles becoming coated with it carry their burden of 
salt around the world. The rain brings to earth now more, 
now less of this salted dust, each region receiving in the 
course of the year an amount fairly proportional to its dis- 
tance from the seacoast and to the rainfall. No mountain 
lake or stream has yet been found free from this element. 
Where evaporation and rainfall nearly balance, the normal 
chlorine will be that of the rain for the year, but where evapo- 
ration is in excess it may exceed that for any given year. In 
the absence of salt-springs and industries using much salt, 
the source of chlorine in excess of the normal is the do- 
mestic life of man. Mr. F. P. Stearns has estimated that the 
chlorine in the drainage of any watershed is increased one- 
tenth part per million by 20 inhabitants. 

Chlorine may serve to prove not only the presence but 
the amount of sewage pollution in any case where the other 
factors are known. Otherwise chlorine has no sanitary 
significance. 

Of the mineral constituents in waters there is little to 
say except that, like climate, water is to be taken as it is 
found — hard, high in mineral matters if derived from a lime- 
stone region, soft if from archean formations. Physicians are 
not agreed as to the effects of hard water, or of the brown 
soft waters. 

Fortunately the human system possesses remarkable 
adaptability, so that if slowly accustomed to a given condi- 
tion, as we have seen in the case of air, and as we shall have 



60 AIR, WATER, AND FOOD. 

occasion to remark when food is considered, it can safely 
bear what would be a serious shock if suddenly encountered 
from an opposite condition. Natives of a hard-water region 
are made ill on coming to a soft-water region, and vice versa. 
Inhabitants of a city with a polluted water-supply seem to 
acquire a certain immunity. 

The safety from organic contamination secured by the 
use of distilled water has brought up the question of a pos- 
sible danger in too little mineral contents for the best cellular 
interchange wherein lies life. 

With the superabundance of mineral salts in ordinary 
diet, there would seem to be little cause for alarm; but if the 
food were poor in these substances, it is quite conceivable 
that evil results might follow a free use of distilled water. 

A word as to the care of water in the house may not 
seem amiss, in view of the tendency it has to absorb gases, 
to collect dust, to favor chemical and vital changes, to dis- 
solve metals. 

Too great care cannot be taken in all these directions to 
secure water freshly drawn from the main pipe beyond the 
lead or brass house-pipes and to avoid those traps for the un- 
wary householders — faucet filters. 

When the water-supply is cafe, but warm and flat to the 
taste, ice is frequently used to cool it. 

Much has been said about the dangers of ice when used 
in drinking-water and on or about food. The latter is prob- 
ably the most serious danger, since people are not so careful 
about the quality of ice for that purpose. 

Certain rules may be broadly stated as guides to the 
householder: 

Crystal-clear ice, free from crevices, bubbles, etc., is 
probably pure, for it has been formed from slow freezing in 
a thin layer, over a deep mass of water, as 20 to 30 inches of 




STATE BOARD OF HEALTH 

MAP OF THE 

STATE OF MASSACHUSETTS. "^1"; 



SHOWING 



NORMAL CHLORINE. 



WATER: SOURCE, PROPERTIES, AND RELATION TO LIFE. 6 1 

ice in a pond 40 or 60 feet deep. In this case the impuri- 
ties have been excluded. This crystal ice is impermeable to 
air and therefore to what air carries, and of course to water 
and what it carries. 

An equally safe rule is to discard all ," snow-ice " made 
from snow saturated with water. 



CHAPTER VI. 

THE PROBLEM OF SAFE AND ACCEPTABLE WATER AND THE 
INTERPRETATION OF ANALYSES. 

(Fro?n the Chemist's Standpoint.) 

From what has been said it will be evident that the prob- 
lem of safe water for domestic use is not so much concerned 
with the water itself as with its property as a carrier and its 
part in chemical changes. 

We have seen how a great variety of vegetable and ani- 
mal matter finds its way into the water of a settled region; 
and as it is constantly being transformed from one form to 
another by the agency of multitudes of organisms, it is evi- 
dent that the exigencies of modern life render impossible the 
exclusive use of water of great organic purity. It is useless, 
therefore, to fight over again the battles of the past as to the 
source and kind of " organic matter " in water. 

We have also seen that it is not the mere presence of 
compounds of carbon, hydrogen, and nitrogen in drinking- 
water which gives the element of danger. It is not even 
the fact that these have taken part in animal life; fish and 
frogs continually die in ponds and streams, to say nothing 
of countless cyclops and mosquito larvae. Well authenti- 
cated cases are on record in which one drink of a polluted 
water has proved fatal; while, on the other hand, it is equally 
sure that highly contaminated water has been used with ap- 
parent impunity. 

62 



water: the problem of safe water. 63 

When water has received excreta of diseased human 
beings, disease-germs are very likely to be conveyed by it 
to other human beings. In a city there are always cases of 
disease, therefore all city sewage is to be considered danger- 
ous. But besides the living germs there are other accom- 
paniments of decaying organic matter which, when in con- 
centrated form, sometimes show toxic properties. Certain 
facts and many conjectures lead to the conclusion that a 
water is " safe " only when free from decaying substances. 

Along with the millions of harmless micro-organisms 
engaged in the work of conversion there may be a few score 
inimical to the health of man, and for the education of the 
still skeptical public it is often advisable to speak somewhat 
strongly of the possible dangers from water-borne disease- 
germs. 

Nitrogen as the Essential Element in Living Matter. — All 
organisms from the lowest to the highest thrive only in the 
presence of food; therefore only that organic matter which 
serves to support life or which, as a product of life, may be 
deleterious to man is rightly to be held as dangerous. The 
element common to both kinds is nitrogen; therefore the 
water-analyst seeks evidence not only of its presence or ab- 
sence, but of the forms in which it is found and their relation 
to one another. It may be assumed that any water which 
shows no change in the relative amount of its nitrogenous 
compounds at the end of a week either does not contain the 
organisms necessary to effect this change or is wanting in 
the food upon which they can thrive. As, however, it is 
inconvenient to wait a week before deciding this point, other 
methods are used. The so-called albuminoid ammonia is 
supposed to indicate the amount of decomposable nitrogen- 
ous matter, but, as a matter of fact, taken by itself it gives 
little information of value. While its absence is conclusive, 



k" 






64 AIR, WATER, AND FOOD. 

its presence is not equally so; but a proof of its variability 
from day to day is really valuable. Whether used in the final 
interpretation or not, " organic nitrogen " (or that portion 
of it appearing as albuminoid ammonia) is always deter- 
mined, together with the other forms, as soon as the sample is 
received. 

A nitrogenous organic compound is dangerous from one 
of two causes: first, because it is already decaying and har- 
bors pathogenic germs or is giving off toxines; or, second, 
because it will furnish food for a further development of bac- 
terial life. 

As to its derivation from animal or from vegetable mat- 
ter, there need be little discussion, especially since the recog- 
nition of the high nitrogenous content of the blue-green 
algae and the nitrogenous character of " soil-humus " and 
the close approximation of animal and vegetable protoplasm. 
But it is most important to know if it is stable, since one of 
the best aphorisms ever contributed to the literature of water- 
analysis is given by Dr. Drown's statement, " A state of 
change is a state of danger." 

Results of the Decay of Nitrogenous Organic Matter. — The 
products of the first stage of decay of this class of organic 
matter are carbon dioxide and ammonia. It is to the 
latter that we turn for the proofs sought, by reason of the 
methods at hand for detecting such small amounts as one 
part in a billion parts of water, and because it is for the nitro- 
gen compound that we seek. 

The mere presence of free ammonia is not a sufficient in- 
dication of recent pollution from human sources. Rain-water, 
as shown in Table III, contains considerable quantities; 
decaying blue-green algse furnish it in still larger amounts, 
and moreover it offers acceptable food to plant-life and may 
therefore disappear in the form of combined nitrogen. 



water: the problem of safe water. 65 

Nevertheless, it is to be held as one of the chief witnesses, for 
it is found in sewage in a thousand times the quantity in 
which it occurs in ordinary potable water. While putrefac- 
tive decay takes place by stages, the lines of division are not 
sharply drawn, and nitrites, the result of the second stage, may 
be and usually are found in polluted waters together with 
ammonia. So frequently is this the case that it is considered 
circumstantial evidence sufficient to convict when both am- 
monia and nitrites are found together. (See Tables V and 
VI, p. 199.) 

The reason is not far to seek. Both are not only prod- 
ucts of decay, but both are in that unstable condition which 
indicates active processes, and which therefore means the 
presence of micro-organisms. Certain exceptions will be 
noted later. 

The fourth form of nitrogen, that found in nitrates, is no 
longer classed as organic; it is now become food for green 
plants and cannot nourish the class to which bacteria and 
pathogenic germs belong, hence it is fair to presume that for 
lack of food the latter have succumbed or have been other- 
wise removed. The value of this test is the proof it sometimes 
furnishes of previous sewage pollution, since the nitrogen 
present in excess of that brought down by rain must have 
been furnished either by fertilizers, by decaying matter, or by 
sewage. (See Tables V and VI, p. 199.) 

Organic Carbon. — Since by far the largest constituent of 
organic matter is carbon, some fifty per cent., it might seem 
as if this was the best indication of pollution. Indeed, it was 
formerly so considered, and many methods have been de- 
vised to show its presence quantitatively. As our knowledge 
of the slight differences between many forms of animal and 
vegetable substances grows, the probability of any conclusive 
evidence from this source, either as to past history or presen h 



66 AIR, WATER, AND FOOD. 

condition, decreases. In short, although for many years 
water-analysts have been striving to perfect methods of de- 
tecting certain substances and certain organisms, it would 
seem as if they were no nearer a discovery of one simple de- 
cisive test, but, in most cases, were driven to a somewhat 
elaborate examination in which one test only furnishes one 
link in the chain of evidence. 

Sanitary Analysis. — The examination of a water to deter- 
mine its safety for domestic use is called a sanitary analysis, 
in distinction from that examination which determines its 
fitness for manufacturing purposes, for use in steam-boilers, 
or its medicinal value. 

Four points are to be determined: First, the amount, if 
any, of organic matter in a living or dead condition, sus- 
pended or dissolved in the water; second, the amount and 
character of the products of decomposition of organic mat- 
ter, and their relative proportions to one another; third, the 
stability of the undecomposed organic substances; fourth, 
the amount of certain mineral substances dissolved. From 
these results we draw conclusions as to the present condition 
and past history of the water. These conclusions are not in- 
fallible, but there are enough unavoidable risks in human 
life without taking unnecessary ones; and if pollution is 
proved, the cause should be removed or the supply aban- 
doned. 

Preliminary Inspection. — So long as the eye can re-enforce 
the other tests and the whole course of the water may be 
clearly traced, it is comparatively easy to judge of the charac- 
ter of a supply and of its safety for human use; but when a 
hole in the ground is the visible source, or the actual history 
of the water is hidden in unknown distances and depths, the 
diagnosis is more difficult. 

First, the geological horizon and superficial soil must be 



__ 



water: the problem of safe water. 67 

studied; the direction and flow of underground water, not the 
slope of the surface only; the possible sources of danger, 
occasional as well as constant, within at least a quarter of a 
mile radius. The composition of unpolluted water of the 
same region should always be at hand for consultation. 

Safe Water. — As has been said, we can no longer require 
pure water; the most that we can demand is that the supply 
shall be safe. To the uninitiated one sample of clear, color- 
less water seems very like any other. The safe, colored or 
muddy water of a stream or pond seems less desirable than 
the clear, cold water of a badly polluted well. 

A water may be normally safe and yet, from exceptional 
circumstances, be for a time a source of danger. In one case 
the mouth of a well at a factory was overflowed by a con- 
taminated brook raised above its usual level by a heavy 
shower for half an hour only. Some thirty cases of typhoid 
fever resulted, so close to one another and so suddenly ceas- 
ing as to leave no doubt of the fact that for only a few hours 
was the water unsafe. How, then, shall a chemist tell if at 
some past time a water may have been or at some future time 
may become a source of disease? Only by carefully weigh- 
ing all the testimony attainable — ocular, chemical, biological, 
bacteriological — in the light of past experience. 

The day of the vest-pocket sample, usually in a flavoring- 
extract bottle, cork and all, is nearly past, but that of the 
fruit-jar, with a sticky rubber ring and corroded zinc top, is 
still with us. That admiration for chemical knowledge and 
belief in chemical clairvoyance which expects the chemist to 
decide from a sample while you wait if a certain water caused 
the death of a person a month since in a distant town under 
unknown conditions is very trying to the man who knows his 
own limitations. 

The market value of an analysis cannot well be appre- 



68 AIR, WATER, AND FOOD. 

dated until a juster estimate of the professional training o£ 
the analyst is a part of common knowledge. 

Safe and Acceptable Water. — It is not enough that a 
supply shall be free to-day from disease-germs; it should re- 
main free from changes for a reasonable period of time. 
Therefore the advice desired by the towns seeking for sup- 
plies implies much more than mere analysis; it includes esti- 
mates of future changes, of variations due to possible further 
developments, and of the effect of these variations on accept- 
ability as well as safety. 

To be fully acceptable, a water should be free from color,, 
odor, turbidity, sediment, and of a uniform temperature so 
low as to admit of use without ice. Only such water as has 
been earth-filtered and earth-cooled can meet this demand, 
but the supply of this class is becoming drawn upon to its 
limit; besides there are difficulties in the conveyance and 
storage of ground-water which offset many of its advantages. 

From the foregoing paragraphs it will be seen not only 
that waters carry every possible degree of safety or danger 
according to the country they drain, the number and habits 
of the people living on the watershed, and the presence or 
absence of factories, slaughter-houses, etc., but that many 
elements enter into the judgment of a water-supply, and how 
different these elements are in different waters. Safe water 
is that which carries neither seeds of disease nor such sub- 
stances as are deleterious in any way to mankind in general. 

A brown water may yield 20 parts per million organic 
matter and show 10 parts oxygen consumed, and yet be a. 
safe and wholesome water. A ground-water may show 5 
parts nitrates, and yet for ten or twenty years prove a safe 
supply. 

Since, however, water is so universally made a carrier of 
refuse, it is difficult to find a stream or well which fulfils the 



water: the problem of safe water. 69 

above exacting requirements, and a compromise is made 
which sets certain arbitrary limits and so keeps the chances 
small. Such limits are very misleading of themselves, espe- 
cially if used over a wide extent of territory. The English 
standards, for instance, are not applicable to eastern North 
America. Only a study of all local conditions and a wise in- 
terpretation of all results can make standard figures of any 
significance. This is true, also, of bacterial results in surface- 
waters. In the natural condition of lakes and streams there 
are so many varieties of bacteria present and in such varying 
numbers, according to wind and rain and watershed, that 
taken alone the numerical count gives no more convincing 
proof than is found in chemical figures. 

While it is quite within the limits of possibility that a 
culture-tube of typhoid bacilli might be emptied into the 
middle of a river or be washed into a reservoir, and chemical 
analysis give no sign, yet no continuous natural means of 
contamination is known which is not accompanied by sub- 
stances readily detected by suitable chemical examination. 
In either case an epidemic may or may not result, dependent 
upon causes other than the mere presence or absence of the 
micro-organisms. 

If drainage from a house or barn is seen entering a 
stream, it does not need a dozen plate-cultures to prove that 
there is possible danger. Such tests may, however, when 
used with skill, serve to trace contamination back to its 
source, and is another means at the service of the trained 
water-works superintendent whereby he can keep a close 
watch over the character of his supply. 

As a means of control of the efficiency of filter-plants the 
bacterial examination is invaluable, and as a knowledge of 
the forms which accompany pathogenic germs becomes more 
certain the value of these tests will increase, even if the 



JO AIR, WATER, AND FOOD. 

classification and identification is not perfected to scientific 
accuracy. 

It is one of the penalties of living in a large city that the 
water-supply must of necessity be surface-water which has 
been caught and stored at a distance or that which has been 
filched from a stream, filtered and made passable. Conse- 
quently education must take the place of instinct, and custom 
must make that acceptable which circumstances render 
necessary. 

THE INTERPRETATION OF ANALYSES. 

Experience in cutting through glacial moraines for rail- 
ways or in driving levels for mining operations does not 
qualify a man for exploration of a Babylonian or prehistoric 
mound. Human occupations have left upon the sand and 
clay evidences which, although so slight as to be unnoticed 
by the casual observer, are like an open book to him who 
patiently acquires a knowledge of the meaning of the dis- 
placements, discolorations, and enclosed fragments. Flowing 
water, like sand and clay strata, bears evidences of its previous 
history no less intelligible to him who has the key to the 
cipher and who adds to the keen eye of the detective and 
ready wit of the interpreter the sound judgment of the engi- 
neer. Reasoning upon insufficient premises will as often 
fail in the one case as in the other, while lucky guesses fre- 
quently encourage superficiality in both. 

After the analyst has entered on the blank (page 120) the 
six to ten records needed for a ground-water, or the fifteen 
to twenty for a surface-water; after the columns headed 
' Bacteria, Diatoms, Algse, etc., have been filled in, there still 
remains the summing up of the case by the judge. The 
correct interpretation of results means a knowledge of 
the source, geological horizon, surroundings, probable 



water: the interpretation of analyses. 71 

changes, and the significance of each item in this particular 
case. Each class of water has its own characteristics. The 
presence, in quantity, of any given element is interpreted 
according to the kind of water under consideration. Spring- 
water is, of course, colorless; lake-water of equal safety is 
probably colored. Spring-water must be, as a rule, free from 
ammonia; lake-water may at times contain considerable 
amounts without detracting from its good character. 

Classification of Waters. — To facilitate examination, 
therefore, waters may be divided into three classes: first, 
cistern, brook, pond, and river water — so-called surface- 
water; second, spring and deep-well water; and third, shal- 
low wells and sewage effluents. 

Water of the last two classes has been for greater or less 
periods of time in contact with rock and filtered through 
sand, hence is designated as ground-water. 

A few examples taken from the different kinds of water 
showing the varying conditions to which they are subjected 
may serve to make the rules of interpretation clearer. 

Surface-Waters. — When rain-water falls on slated or 
shingled roofs and is conducted into cisterns, it carries with 
it whatever deposits tave collected, the pollen of forest-trees 
or disease-germs from city slums many miles away; from 
metal roofs it takes either the metal itself or the paint used 
to protect the surface. In all cases, lower forms of animal 
life, small insects, and soot from chimneys may be present. 
These foreign substances should be at once filtered out with- 
out allowing time for organic decay, unless there is an auto- 
matic device for wasting the first washings of the collecting 
surface. There are still substances in solution which would 
be better away; therefore the water is allowed to stand 
quietly in order that the changes may have time to take 
place — to ferment, as it is often technically expressed. After 



72 AIR, WATER, AND FOOD. 

this season of purification the water is again filtered and 
stored ready for use. There is usually color and a little am- 
monia, but rarely nitrates. The soluble metals, if once pres- 
ent, still remain. It goes without saying that all such 
cisterns must be absolutely impervious to surface drainage. 
For lack of one or all of these precautions, cistern-water has 
often been found to be contaminated from cesspools, from 
leaden or painted roofs, or from decaying organic matter. 

Brook-water. — The rain that falls on mountain slopes of 
granitic or other insoluble rocks washes from them whatever 
loose earth may have fallen there, and from the firmly fixed 
lichens the small insects and other animal forms which they 
harbor. These are transported in brooks to the lower lands 
where the organisms decay, the heavier earthy particles fall- 
ing out by the way. 

If the upland rocks and soil yield a portion of mineral 
salts to the water, it may come out clear and colorless even if 
it has not penetrated to an appreciable depth. 

The water from these forest brooks, after remaining im- 
pounded in a clean lake or reservoir, exposed to sunlight and 
air, often becomes the safest source of supply. As with cis- 
terns, so with reservoirs, filtration, natural or artificial, may 
take place previous or subsequent to storage, or both before 
and after. 

Lake or Mixed Water, — Lakes are fed by springs as well 
as by brooks, or by that portion of rainfall which passes a few 
inches below the surface, and is filtered before reaching the 
main body. If the banks are sandy and uninhabited, the 
water will show good effects from this filtration; but if the 
seepage-water comes from a settled country, it will bring 
either ammonia or nitrates. The analysis will quickly show 
this if the water sample can be taken before it has mixed 
with that bearing the spores of plants which are fed by 



water: the interpretation of analyses. 73 

nitrates. Often the very presence of these plants furnishes 

the proof sought. 

River-waters. — A large stream, like the Mississippi, may 

receive the drainage of half a dozen cities a hundred miles 

distant and yet not give conclusive evidence of dangerous 
contamination, while a small river, like the Potomac, may 

become unsafe from the presence of a few villages a dozen 

miles away. 

Northeastern America is so well supplied with uninhab- 
ited high lands for collecting-grounds, and with basins in the 
.glacial drift for storage in natural or artificial lakes, that very 
iew rivers need to be used after they have become polluted. 
The Merrimac and the Hudson are, however, so used. In 
other parts of the country the use of rivers is an increasing 
necessity. 

From every point of view organic matter should be kept 
as far as possible out of running streams which may at any- 
time be needed for public supplies, or the natural purifica- 
tion by algae should precede the final filtration and storage. 
It is quite probable that this double treatment may be more 
frequently required as unpolluted water becomes more 
.scarce. 

What the method of filtration shall be depends upon the 
character of the water, whether clear or turbid with clay, 
whether certainly polluted or only with a remote possibility 
of contamination. Each problem must be studied by itself 
Avithout prejudice in favor of any one method. It is the re- 
sult which must be kept in mind, namely, the furnishing of 
safe and acceptable water to the community. 

Effect of the Storage of Surface-water. — In interpreting 
his results, the analyst should take into account the influence 
wdiich the keeping of water in basins has upon its character. 
Storage of surface-water is of utmost importance in all cases 



74 AIR, WATER, AND FOOD. 

of doubt. Most disease-germs find such water an unfavor- 
able medium for prolonged life, since exposure to sunlight 
soon destroys the darkness-loving bacteria, and a certain 
sterilizing effect results from the growth of green algae, so 
that water considerably polluted becomes purified if given 
time for the various agents to do their work; but time is, 
essential. 

Odors. — For surface-waters one of the links in the chain 
of evidence is found in the odor, cold and hot, which to the 
trained and sensitive nose often gives convincing testimony.. 
A musty odor, unmistakably different from a mouldy vege- 
table smell, betrays sewage contamination even when the 
chemical analysis might not be convincing. This odor is not 
always taken out by filtration, neither is that of certain or- 
ganisms growing in stored water, notably Anabcena and 
Synura. A study of these organisms is invaluable to the 
routine observer who watches the seasonal and annual 
changes in his reservoir. 

Turbidity and Sediment. — The determination of turbid- 
ity and sediment, added to the odor, tells much to the expert, 
but very little to the inexperienced student. Turbidity may 
be due to drainage contamination, to growth of bacteria, to 
clay, to iron, to swarms of micro-organisms. Sediment may 
be sand, zooglea, fragments of plants or animals, or ferric 
oxide. 

Filtration. — The subject of filtration has been so exten- 
sively treated elsewhere that the student is referred to the 
bibliography on page 213. There are cases in which it is 
preferable to run the risk of too much alum in the drinking- 
water, and too much sulphuric acid in boiler feed-water^ 
rather than of too many micro-organisms with the accom- 
panying organic matter. 

It will have been noticed that the ideal natural water is 



water: the interpretation of analyses. 75 

that which has been earth-filtered, and thus all suspended 
matter, including microbes, has been removed. This sup- 
poses that sufficient time has elapsed so that all decomposing 
organic matter has been destroyed. Man tries to imitate 
nature's processes, but expects to accomplish it in moments 
instead of months. 

The era of house-filters, those admirable culture-grounds 
for bacteria, is happily nearly past. Taxpayers are becoming 
convinced that a good original water-supply in competent 
hands is worth paying for. Where straining only is needed, 
a flannel bag washed daily is as efficient as any faucet-filter. 
If the latter takes out color as well, it should be closely 
watched. Water should not be first boiled and then filtered, 
but first filtered and then boiled. 

Summary. — Surface-water. — In general it may be said 
that the waters of the first class found in New England are 
generally more or less colored, and contain more or less sus- 
pended organic life and its debris, which often impart a de- 
cided odor to the water. These waters, draining for the most 
part wooded and sparsely populated regions, are low in free 
ammonia, nitrates, and nitrites; low, also, in mineral salts, 
and with only a slight excess of chlorine over the normal. 
They are usually high in organic matter and albuminoid am- 
monia even when entirely free from pollution. 

In other parts of the United States surface-waters may be 
low in color, but with much suspended clay and silt, and may 
hold in solution notable quantities of mineral salts. The 
latter aid greatly in the clarification by artificial filtration, 
which is so often rendered necessary by the excessive turbid- 
ity even if not by sewage contamination. 

In Table IV, page 198, will be found examples showing 
at a glance how profoundly the character of a water is affected 
by the geological horizon, whether its source is in the glacial 



j6 AIR, WATER, AND FOOD. 

drift of the Appalachian region, or in the limestone of the 
Hudson River Valley, or in the saline deposits of the sub- 
sided areas. 

Deep Wells and Springs. — The waters of the second class 
are derived from the depths of the earth, far below any pos- 
sible surface contamination, and have long been imprisoned 
in the dark and cold, and often subjected to great pressure, 
The influence of pressure on organisms has not been entirely 
worked out, but from what is known it is probably very un- 
favorable to the life of the lower organisms. The results of 
many bacterial examinations have been vitiated by the diffi- 
culty of securing a sample from great depths without con- 
tamination by surface exposure — pipes open to the air har- 
boring many forms of life. 

Deep wells, 700 feet and more, are not likely to be dan- 
gerous. They may often contain ammonia from prehistoric 
coal-fields or tertiary deposits, but rarely nitrates. This is 
accounted for by the fact that " the result of the changes of 
the nitrogenous organic substances which fall into the earth 
is, without doubt, frequently the formation of gaseous nitro- 
gen." Also, that " salts of nitric acid on penetrating into 
the depths of the earth give up their oxygen. " * 

Owing to their long sojourn in the depths of the earth, 
these waters are higher in mineral substances than surface- 
waters. Since their origin is unknown, the chlorine cannot 
be correctly gauged, especially as there are saline waters deep 
down in rock cavities in all parts of the world. 

It is usually believed that these deep wells furnish a safe, 
palatable water when the kind and amount of mineral matter 
is not objectionable. 

Shallow Wells. — It is not to be wondered at that waters 

* Mendeleeff : "Chemistry," p. 223. 



WATER: THE INTERPRETATION OF ANALYSES. 77 

of the third class — ground-water, taken from just beneath 
the surface layers of the soil — should contain many sub- 
stances foreign to the waters about them as well as to those 
at greater depths. The shallow wells, which are practically 
more or less diluted sewage effluents, present the greatest 
variety. They may be clear and colorless and show as great 
organic purity as the best mountain spring. In other cases, 
the overworked filter permits the passage of organisms and 
undecomposed material. In either case there will be found 
those compounds which, being soluble and stable, are car- 
ried with the water as signs to be read by him who knows the 
language. A complete history of each specimen of this class 
of ground-water is desirable, and with sufficient patience 
and care it may be obtained with reasonable accuracy, if the 
principles governing the circulation of water and the changes 
of the organic matter it carries be kept well in mind. 

It is certain at once that absence of color, of organic mat- 
ter in any form, and of odor should be insisted upon, for 
ground-water is filtered water and the filter should be doing 
its work. 

A modicum of geological knowledge is essential, as the 
presence of shaly or slaty rock will permit the passage into 
underground water of surface drainage with less purification 
than will a granite or sandstone region. A clayey soil is a less 
efficient filter than a sandy loam and permits the pollution 
to travel farther. 

Nitrogen in Well-water — It may be taken as an axiom 
that the only form of nitrogen permissible in a good ground- 
water is that of nitrates, a fully oxidized or mineralized food 
for green plants. If nitrites are also present, a source of 
pollution is at hand, for, as has been said, nitrites indicate 
either a stage of oxidation not completed or one of reduction 
from nitrates in the presence of organic matter. If free am- 



y8 AIR, WATER, AND FOOD. 

monia be present, it is safe to say that the source is not only 
near but in actual contact, since but a few hours' time is 
needed to oxidize the ammonia in any soil not waterlogged. 
It may also be pretty safe to assume that bacteria are present, 
since ammonia is the first stage of that decomposition which 
they accompany. It is the part of prudence, therefore, to 
avoid any water which contains both free ammonia and 
nitrites above .200 or .300 parts per million of the first, and 
.020 or .030 of the second. 

The absorption of nitrogen by plants is rarely complete, 
so that it usually appears in far larger quantities in contami- 
nated ground-waters than could be obtained from purified 
rain-water. The leaching cesspool discharges its liquid con- 
tents' below the zone of green-plant life; fertilized soil also 
yields a portion of its food value to the lower layers. A 
small portion of the nitrogen of vegetable origin may appear 
as nitrates, but only as a derivative of soil rich in humus is it 
likely to play any considerable part. In eastern America 
nitrates above 0.5 parts per million would arouse suspicion, 
and above 5 parts would in most cases prove previous pollu- 
tion. 

It is evident that in the use of nitrogen as an indicator of 
the conditions of a water we are limited, by the changeful 
character of the compounds, to certain not-to-be-mistaken 
amounts, and that in the majority of cases the evidence given 
is not decisive. 

Chlorine in Well-water. — Fortunately there is another ele- 
ment not so eagerly sought for by plants and not liable to so 
many transformations. Thanks to the great solubility of its 
common compounds and to their stability, chlorine, once a 
constituent of a given body of water, is not extracted there- 
from and remains as a telltale to reveal the past history of a 
stream or spring. If a man is judged by the company he 



WATER: THE INTERPRETATION OF ANALYSES. 79 

keeps, much more a water-supply. From sewage all the 
nitrogen may be removed and the chlorine still remain. 

But in order to use this information with any degree of 
certainty the normal chlorine of the locality must be known. 
If a map showing isochlors has been made of the region or 
State, and if there are no geological deposits to interfere, this 
is easy; but if the chemist or engineer has an unknown coun- 
try to report upon, it will be necessary to examine the local 
conditions and to choose six, eight, or ten samples of prob- 
able freedom from contamination and to test them for com- 
parison. The sources of the excess of chlorine over the 
normal are usually the sink-drain with its burden of salted 
water from domestic operations; the house-drain, with its 
chlorine-containing excreta; and the stable-drain, with a 
slight chlorine content in comparison with the other two. 

Mineral Substances. — Since water Is a universal solvent, 
it is not surprising to find considerable amounts of mineral 
matter in the two columns " Total Solid Residue on Evapo- 
ration " and " Hardness. " How much calcium sulphate or 
magnesium chloride or other soluble mineral is allowable in 
a potable water is for the physician rather than the chemist 
to say. As has been said, the human system possesses great 
adaptability, not only for different foods, but for mineral sub- 
stances water-carried. Not so the steam-boiler or the laundry- 
tub, which reacts very sensitively and affects the pockets 
of the consumers. In a region of soft water, high solids 
with chlorine and nitrates indicate sewage pollution. 
Silica is much more commonly present even in surface- 
waters than is often supposed. What its effect may be is 
unknown. Iron is not uncommonly found in combination 
with organic matter in either surface or imperfectly filtered 
waters in contact with soils poor in calcium salts. It is fre- 
quently accompanied by free ammonia, which causes an 



8o 

abundant growth of Crenothrix. It is also present in deep 
wells in the form of carbonate, which precipitates on exposure 
to warm air. 

In a considerable number of cases of public water-supply 
there is a mixture of surface and ground water which com- 
plicates the verdict, requiring a most delicate balancing of 
probabilities. The mineral contents often aid in this deci- 
sion. Well-waters, too, are often exposed to surface-wash 
because of poor protection at the mouth. Cyclops or other 
surface-water organisms often indicate this. 

Water-pipes. — After all, if the pipes conveying the water 
are of lead or brass, an additional danger appears. Gen- 
erally speaking, the purer the water the greater the risk. 
No common metal seems to withstand the action of soft 
water; six to eight years being the average age of galvanized 
pipe, and eight to ten of iron pipe. It would seem as if 
cement-lined pipe must come into greater use until some 
kind of glass is invented which will withstand this corrosive 
action and yet admit of plumber's connections. 

Value of Tests. — It is often asked if some tests cannot be 
made by the ordinary person of average intelligence which 
will enable him to tell the quality of a water as well as the 
expert to whom he pays ten or twenty dollars for an opinion. 
A careful perusal of the preceding pages will have answered 
the question in the negative. There is no assay of water as 
there is of gold and silver. Not one but ten or twenty tests 
must be made. Not only must the tests be made with the 
utmost care and cleanliness of person, utensils, and room, but 
the results must be studied in the light of other experience 
and other knowledge, geological and biological, and after 
all this is done there is an array of circumstantial evidence 
which must be carefully weighed by one whose judgment and 
experience ena'ble him to read clearly where another might 



water: the interpretation of analyses. Si 

see nothing. The value of a water-analysis is in direct pro- 
portion to the knowledge and experience of the one who 
interprets it. Clinical skill in addition to theoretical knowl- 
edge is required to interpret the figures obtained in the course 
of a water-analysis, as in the symptoms of a disease: and the 
analogy goes still further, for as some diseases are clearly 
defined, others are so complicated that only those who have 
had long experience can outline a safe course, of treatment; 
so some waters bear the marks of their character so plainly 
as not to admit of mistake, while others require most careful 
study. For these reasons the value of water-analysis should 
not be decried because the fears aroused by reports given by 
unskilled analysts prove groundless, any more than the prac- 
tice of medicine should be discarded because inexperienced 
men make mistakes. 

Is the water in any given case safe for drinking? To an- 
swer this question there is needed a knowledge wider than a 
chemist's of the relation of decaying organic matter and of 
the germ-carrying power of water to outbreaks of disease. 
There must be added the knowledge of the biologist, the en- 
gineer, and the sanitarian. 



CHAPTER VII. 



ANALYTICAL METHODS. 



General Statements. — Water-analysis cannot be carried on 
in an ordinary laboratory. In order to obtain satisfactory 
results it is necessary to have a room set apart for the pur- 
pose, and to exclude rigidly all operations which tend to the 
production of fumes or dust. Where such minute traces of 
substances are dealt with as in water-analysis, too much care 
cannot be taken to insure the absolute cleanliness of the ap 
paratus and the surroundings. It is desirable that the room 
be well lighted, and if possible the windows should face 
toward the north. 

The methods for the examination of water which are de- 
scribed in this chapter by no means comprise all that are in 
use. The directions are given for the use of students in our 
own laboratory under the conditions obtaining, i.e., of large 
classes and of several courses of study, with especial reference 
to educational rather than purely technical needs, and in some 
cases, no doubt, the traditions of thirty years may have unduly 
persisted. The methods have been so selected as to intro- 
duce a variety of apparatus and to illustrate principles. They 
have also been subjected to a thorough test in meeting the 
demands of practical work. 

Collection of Samples. — For the collection of water sam- 
ples, glass-stoppered bottles of about a gallon capacity are 
best. Those used in this laboratory are of white glass, fifteen 
inches high to the top of the stopper, five and a half inches 



water: analytical methods. 83 

in diameter, and weigh about three pounds. They have flat, 
mushroom stoppers, on which is engraved a number to corre- 
spond with that on the bottle. The bottles, before being 
sent out, are thoroughly cleaned with potassium bichromate 
and sulphuric acid, washed with distilled water and dried. If 
glass-stoppered bottles are not at hand, new demijohns fitted 
with new corks may be used. A glass bottle or a demijohn 
is much to be preferred to an earthenware jug, because, if for 
no other reason, it is so much easier to be sure that the interior 
is clean. It should always be borne in mind that in water- 
analysis the question is one of very minute quantities of mate- 
rial, and that the methods to be employed are extremely 
delicate. Hence, in the case of many waters, careless hand- 
ling of the sample would contaminate the water to a sufficient 
extent to render valueless the results obtained in the labora- 
tory. In collecting samples, the following directions should 
be closely followed: * 

Directions for Collecting Samples for Analysis — From 
a Water-tap. — Let the water run freely from the tap for a 
few minutes 'before collecting the sample. Then place the 
bottle directly under the tap and rinse it out with the water 
three times, pouring out the water completely each time. 
Place it again under the tap; fill it to overflowing and pour 
out a small quantity so that there shall be left an air-space 
under the stopper of about an inch. Rinse off the stopper 
with flowing water; put it into the bottle while still wet and 
secure it by tying over it a clean piece of cotton cloth. Seal 
the ends of the string on the top of the stopper. Under no 
circumstances touch the inside of the neck of the bottle or 
the stem of the stopper with the hand, or wipe it with a 
cloth. 

From a Stream, Pond, or Reservoir. — Rinse the bottle and 

* Ann. Rep. Mass. State Board of Health, 1890, p. 520. 



84 AIR, WATER, AND FOOD. 

stopper with the water, if this can be done without stirring: 
up the sediment on the bottom. Then sink the bottle, with 
the stopper in place, entirely beneath the surface of the water 
and take out the stopper at a distance of twelve inches or 
more below the surface. When the bottle is full replace the 
stopper, below the surface if possible, and secure it as directed, 
above. It will be found convenient, in taking samples in 
this way, to have the bottle weighted so that it will sink be- 
low the surface, and to remove the stopper by a cord. It is, 
important that the sample should be obtained free from the 
sediment at the bottom of a stream and from the scum oa 
the surface. If a stream should not be deep enough to admit 
of this method of taking a sample, dip up the water with an 
absolutely clean vessel and pour it into the bottle after the 
latter has been rinsed. 

The sample of water should be collected immediately be- 
fore shipping by express, so that as little time as possible 
shall intervene between the collection of the sample and its 
examination. All possible information should be furnished 
concerning the source of the water and of possible sources of 
contamination. For example, in the case of a well, the prox- 
imity of dwellings, cesspools, or drains should be recorded, 
and the character and slope of the soil, whether toward or 
away from the well, should be noted. In the case of a sur- 
face-water, mention any abnormal or unusual conditions; as, 
for instance, if the streams or ponds are swollen by recent 
heavy rains, or are unusually low in consequence of prolonged 
drought, or if there be a great deal of vegetable growth in or 
on the surface of the water. Record, in short, any circum- 
stantial evidence which by any possibility may aid in the final 
judgment. 

The question of proper collection of samples is an impor- 
tant one, and the chemist is perfectly justified in refusing to> 



water: analytical methods. 85 

give an opinion in regard to the purity of a water which he 
has not himself collected. The ignorance and carelessness 
shown by people who send samples for analysis are often- 
times quite amusing. Samples have been received at this 
laboratory in almost every kind of container imaginable, from 
an imperfectly rinsed whisky-bottle to a discarded syrup-jug, 
with about an inch of maple sugar in the bottom. One sam- 
ple was sent all the way from Georgia in a stone jug with a 
corn-cob inserted for a stopper. Others are received with 
the stopper carefully (?) protected by a mass of sealing-wax 
or candle-grease. A favorite way is to send the sample in a 
fruit-jar packed in sawdust or straw. Opinions evidently 
differ greatly, too, in regard to the size of sample that is 
needed. It is no uncommon occurrence to have a person 
come into the laboratory with the remark, " Here is a sample 
of water that I want analyzed," supplemented by the produc- 
tion from a coat-pocket of a homoeopathic vial or a sample 
of half a pint or so of water. Of course, in cases like these 
practically nothing can be done. 

Preparation of the Sample for Analysis. — Since changes 
in the composition of a contaminated water are constantly 
going on, the analysis of the sample should be begun without 
delay. The bottle is held under the tap, and the neck and 
stopper are washed free from adhering dust. The stopper is 
rinsed off with some of the water from the bottle. Qualita- 
tive tests should be made for ammonia, nitrites and chlorine. 
With waters containing much suspended matter, and in the 
case of surface-waters in which it is desired to distinguish 
between the organic matter in solution and that in suspen- 
sion, a portion of the water should be filtered. In most 
cases the suspended matter can be removed by filtration 
through paper. For this purpose only the best Swedish 
filter-paper should be used, and the filters should be first 



•86 



AIR, WATER, AND FOOD. 



thoroughly washed with ammonia-free water. With some 
waters containing very finely divided clay in suspension, fil- 
tration through paper will not be satisfactory, and the sample 
must be filtered by suction through a cylinder of unglazed 
porcelain, such as an ordinary Chamberland-Pasteur filter- 
tube. In the filtered water it is customary to determine the 
dissolved solids, the albuminoid ammonia, or the organic 
nitrogen, and the color. 

Determination of Free and Albuminoid Ammonia.— 
Apparatus. — The apparatus used for the determination of 

ammonia is that shown 
in Fig. 4. It consists 
of a round-bottomed 
flask of 900 c.c. capaci- 
ty, with square shoul- 
ders and a narrow neck 
five inches long, and an 
ordinary Liebig con- 
denser fitted with an 
inner tube of block tin, 
3 / 16 of an inch in diame- 
ter. The flask is closed 
by a cork carrying a 
glass tube bent nearly at 
right angles, which 
slips for some distance 
within the tin tube of 
the condenser. A tight 
joint is made by means 
of a large cork, which 
is shown in section in 
Fig. 5. The large cork 
serves the double purpose of making a tight joint with the 




Fig. 4. 



ScaleJHin^lfoot., 

■Apparatus for Ammonia Dis- 
tillation. 



water: analytical methods. 



87 



condenser and also as a convenient means for handling the 
small glass tube. In order to remove the cork from the dis- 
tilling-flask, the glass tube carrying it is simply turned to one 
side, using the large cork as a pivot. The flasks are heated 
with the free flame of a Bunsen burner. 

New flasks are treated with boiling dilute sulphuric acid 
and potassium bichromate before they are used. New corks 
should be steamed out for one or two hours. A good, sound 
cork will last for several months with daily use. The dis- 




CORK JOINT 

Full Size 

Fig. 5. 

tillates are received into small 50-c.c. flasks and poured into 
Nessler tubes for nesslerization. The Nessler tubes are 11 
inches long and f-inch internal diameter, the 50-c.c. mark 
being about two inches from the top. It is possible to so 
arrange the apparatus as to collect the distillates directly in 
the Nessler tubes where only one or two samples are exam- 
ined at a time. For class work the compact form of appara- 
tus similar to that used in agricultural laboratories for the 
Kjeldahl determination is not so suitable. 

Directions. — Free the apparatus from ammonia by dis- 
tilling off the water in the flask, testing each 50-c.c. portion 
of the distillate until no color is given with the Nessler re- 
agent. When the distillate is free from ammonia, pour the 



88 AIR, WATER, AND FOOD. 

water left in the flasks into the bottle marked " Ammonia- 
free Residues." 

Shake the bottle thoroughly to mix the sample, and 
measure out in a calibrated flask a portion, usually 500 c.c, 
for the ammonia, the amount taken depending upon the re- 
sult of the qualitative test. Pour this into the distilling- 
flask, and distil over three portions of 50 c.c. each into the 
graduated flasks. Regulate the height of the flame so that 
the time of distilling 50 c.c. shall be not more than eight and 
not less than five minutes. 

After the free ammonia has been distilled off, allow the 
contents of the flask to cool slightly; then add 40 c.c. of alka- 
line permanganate through a funnel, taking care that none 
of the alkaline solution touches the neck of the flask, and pro- 
ceed with the distillation of the albuminoid ammonia; that is 
to say, the determination of the nitrogen of the undecomposed 
organic matter. With colored surface-waters distil off five 
portions of 50 c.c. each; with waters of low organic content 
three or four portions will suffice. 

It is almost impossible to convert all of the organic nitro- 
gen into ammonia by boiling with alkaline permanganate, 
the amount of ammonia which is thus obtained depending 
upon the concentration of the solution and the rate of boil- 
ing. In order that the albuminoid ammonia shall bear some 
definite relation to the total organic nitrogen it is necessary 
that these conditions shall be duplicated as nearly as possible 
in different determinations; that is, the alkaline permanga- 
nate must be added to a definite volume of the water, and 
the boiling must be carried on at a definite rate. Some of 
the highly colored surface-waters give up their nitrogen very 
slowly by this treatment, so that to distil off all the albumin- 
oid ammonia which these waters are capable of vieldingf 
would be an almost endless task. It is much better to He 



water: analytical methods. 89 

content with the comparative results which can be obtained 
hy carrying out successive determinations under similar con- 
ditions. 

Have the Nessler tubes clean and thoroughly rinsed, and 
pour into them the contents of the 50-c.c. receiving-flasks. 
Prepare the standards by adding to Nessler tubes nearly filled 
with ammonia-free water varying quantities of the standard 
ammonium chloride solution; for instance, 0.1, 0.3, 0.5, 0.7, 
1.0, 1.3, 1.5, 2.0, 2.5, 4.0, 6.0 c.c. The standard ammonium 
chloride solution contains .00001 gram N in one cubic centi- 
meter. 

Mix the contents of the tubes by rotating them between 
the palms of the hands (never shake them like a test-tube or 
stir them with a rod), allow them to stand for two or three 
minutes and add 1 c.c. of the Nessler's reagent to the whole 
set, and to the samples to be tested, as rapidly as possible. 
At the end of ten minutes match the colors and record the 
amount of ammonia. 

As an example of a colored surface-water may be given 
the following results from distilling 500 c.c: 

Free Ammonia. Albuminoid Ammonia. 

1st 50 c.c, 0.7 c.c 1st 50 c.c, 4.5 CC 

2d 50 c.c, 0.3 c.c. 2d 50 c.c, 2.8 CC. 

3d 50 c.c, 0.0 c.c. 3d 50 c.c, 1.5 c.c. 

4th 50 C.C, 1.0 CC. 
5th 50 c.c, 0.5 CC. 



1.0 c.c. 10.3 CC. 

In this case the free ammonia would be 0.020 and the 
albuminoid ammonia .206 parts per million. 

Notes. — When the amount of ammonia shown by the 
qualitative test is high, i.e., shows a color equivalent to 1 c.c. 



go AIR, WATER, AND FOOD. 

of the standard ammonia solution, a less quantity than 500 
c.c. should be taken for the distillation, 100 c.c. or, in the case 
of sewage, even 10 c.c. being diluted to 500 c.c. with water 
free from ammonia. If the waters give much trouble from 
bumping, coarsely crushed pumice may be used in the dis- 
tilling-flask, although it is difficult to keep it pure enough for 
use with waters very low in ammonia. If pumice is used, care 
should be taken that the fragments have rounded corners to 
avoid scratching the glass. Sewage and soils may be dis- 
tilled with steam in the apparatus figured on page 92 under 
the Kjeldahl process. 

In dealing with sewage or sewage effluents, which are 
very high in free ammonia, if the ammonia were collected in 
three portions, so much would distil over in the first portion 
that the color given with Nessler's reagent would often be too 
deep to read or a precipitate might form. To avoid this the 
total distillate of 150 to 175 c.c. is collected in a 200-c.c. grad- 
uated flask, made up to the mark, thoroughly mixed by 
pouring, and then 50 c.c. of it taken for nesslerization. In 
this way the ammonia is distributed more evenly in the dis- 
tillate and the determination is not sacrificed. 

In the case of water from suspicious wells and of sewage 
effluents, about 0.5 gram of freshly ignited sodium carbonate 
should be added before distillation, in order to make sure that 
the reaction of the water is not acid, and to decompose any 
urea which may be present. This will not be necessary with 
ordinary surface-waters, as experience has shown that they 
almost always have a slight alkaline reaction. 

The necessity for the use of soda will be readily seen 
from an inspection of the following results obtained on the 
distillation of bad well-water: 



water: analytical methods. 91 



Withe 


'«£ Soda. 


JFYM .Wa. 


ree NH 3 , 


, Alb. NH 3 . 


Free NH 3 . 


Alb. NH, 


2.0 


7.0 


50 out of 


I.O 


2-5 


3-0 


200 = 4.8 


•7 


3-0 


2.0 
I.O 


Total = 19.2 


•3 



For measuring very deep colors with the Nessler reagent, 
say above 6.0 c.c. of the standard ammonium chloride solu- 
tion, it will often be found convenient to use a pair of 
Hehner's colorimeters, running off a known amount of the 
solution having the deeper color until the colors match. In 
doing this it is important that the color of the standard 
should not differ much from the color of the distillate, for 
the depth of color given by the Nessler reagent is not ex- 
actly proportional to the amount of ammonia alone; that is 
to say, the depth of color obtained by nesslerizing 6.0 c.c of 
ammonia solution is more than twice that obtained wLh 3.0 
c.c. in the same volume of water. 

In order to secure the most accurate results it is impor- 
tant that the temperature of the distillates to be nesslerized 
and of the standards be the same, since the warmer solutions 
give a more intense color with the Nessler reagent. 

The compounds produced by the action of ammonia on 
mercuric solutions are considered as substitutions of 1 Hg 
for 2H in NH 4 , and are called mercur-ammoniums. Tetra- 
mercur-ammonium iodide (NHg 2 I), the compound formed by 
addition of the Nessler reagent, is a brown precipitate, sol- 
uble in excess of KI in the presence of KOH with a brown- 
ish-yellow color proportional within certain limits to the 
n mount of NH 3 : 

NH 3 + (2HgI 2 + 2KI + 3KOH) = NHg 2 I + 5KI + 3H.O. 

The " free ammonia " in all probability does not exist in 

the water in a free state or as the hydroxide; it is probably 



92 



AIR, WATER, AND FOOD. 



present in the form of carbonate or of chloride. When water 
containing these or similar compounds of ammonia is boiled, 
they are decomposed and free ammonia passes off with the 
steam and is found in the distillate; hence the origin of the 
name. 

Determination of Total Organic Nitrogen by the 
Kjeldahl Process — Directions. — Measure 500 c.c. of the 
water into a round-bottomed flask of 750 c.c. capacity and 




Fig. 6. — Apparatus for Distilling Ammonia by Steam. 

boil until about 200 c.c. have been driven off. (The free 
ammonia which is thus expelled may be determined, if de- 
sired, by connecting the flask with a condenser.) Allow the 
water remaining in the flask to cool, and add 10 c.c. of 
pure concentrated sulphuric acid free from nitrogen, Mb?, 



water: analytical methods. 93 

by shaking; place the flask in an inclined position on wire 
gauze under the hood and boil cautiously until the water is 
all driven off. Place a small funnel in the neck of the flask 
to prevent the escape of acid fumes, and continue the heating 
for at least half an hour after the sulphuric acid becomes 
white. Meanwhile rinse out the distilling apparatus (see 
Fig. 6), and free it from ammonia as usual. Then, after the 
acid in the digestion-flask has cooled, rinse down the neck 
of the flask with ioo c.c. of ammonia-free water and attach 
the flask to the distillation apparatus. Add ioo c.c. of 
potassium hydroxide solution through the separatory funnel 
and distil off the ammonia by steam, receiving the distillate 
in a 250-c.c. graduated flask. Conduct the distillation rather 
slowly until the first 50 c.c. have distilled over, then distil 
more rapidly until about 175 c.c. have been collected. Make 
the volume of the distillate up to 250 c.c. with ammonia-free 
water, mix it thoroughly and take 50 c.c. for nesslerization. 

Notes. — The principles involved in- the method consist in 
the oxidation of the carbon and hydrogen of the organic mat- 
ter by boiling sulphuric acid, the nitrogen being converted 
into ammonia and held by the acid as ammonium sulphate. 
The ammonia is then liberated and distilled off from an alka- 
line solution. The use of mercury and of potassium per- 
manganate to assist in the oxidation has been found to be 
unnecessary, as the organic matter in natural waters is much 
more easily oxidized than in other substances, — flour, for in- 
stance. The presence of nitrates and nitrites in waters has 
not been found to interfere with the accurate determination 
of the organic nitrogen. The error which has been found by 
Kjeldahl and Warrington to be caused by the presence of 
nitrates seems to disappear when the organic material is 
diluted to the considerable extent that exists in natural 
waters. The high chlorine found in some well-waters does 



94 AIR, WATER, AND FOOD. 

not interfere with the method to any extent, but this deter- 
mination does not possess much value in this class of waters, 
which are low in organic nitrogen. 

In carrying out the digestion with sulphuric acid, the 
greatest care must be taken to prevent access of ammonia or 
dust from any source. The acid solutions will absorb am- 
monia from the air or from the dust of the laboratory if they 
are allowed to remain uncovered for any length of time. 
This source of error may in some instances be sufficiently 
large to render a determination valueless, even in a room 
which is to all appearances free from ammonia-fumes. 
Hence the operation should, if possible, be carried to com- 
pletion within twenty-four hours, and for every set of deter- 
minations a blank analysis should be made with ammonia- 
free water in order to make a correction for the ammonia in 
the reagents, and for that accidentally introduced during the 
process. 

As the result of many hundred comparative determina- 
tions of thf organic nitrogen and of the albuminoid ammo- 
nia in natural waters which take their origin in the glacial 
drift, it has been found that the nitrogen given by the albu- 
minoid-ammonia process as directed in the previous pages 
is about one-half of the total organic nitrogen as given by the 
Kjeldahl process; in the case of sewages and polluted waters 
it may be only about a third. 

Determination of Nitrogen in the Form of Nitrites. 
— Directions. — When the determination of the free and 
albuminoid ammonia is well under way, the estimation of 
nitrogen in the next stage of decay, that of nitrites, should 
be begun. If the water is colorless, measure out the required 
amount, usually ioo c.c, into a ioo-c.c. tube. If the water 
possesses color which cannot be removed by simple filtra- 
tion, it should be decolorized as follows: Thoroughly rinse 



water: analytical methods. 95 

with the water a 250-c.c. glass-stoppered bottle; pour into 
it about 200 c.c. of the sample, add about 3 c.c. of the milk 
of alumina and shake the bottle vigorously. Let the bottle 
stand for ten or fifteen minutes and filter through a small 
filter which has been thoroughly washed with water free 
from nitrites. Enough should be filtered for both the 
nitrites and nitrates. At the same time, make up stand- 
ards by adding to the tubes containing about 100 c.c. of 
nitrite-free water varying amounts of the standard solution; 
for example, 1.0, 3.0, 5.0, and 10.0 c.c. 

To each of the tubes containing the colorless water, and 
to the standards, add the following reagents in the order 
given: 1 c.c. of hydrochloric acid (1:3), 2 c.c. of sulphanilic 
acid, 2 c.c. of naphtylamine hydrochlorate. Mix thor- 
oughly, and after twenty minutes compare the colors. One 
cubic centimeter of the standard nitrite solution contains 
0.0000001 gram N as nitrite. The determination must be 
completed within half an hour, since the air of a room in 
which gas is burned contains nitrites.* 

Ilosvcty's Modification. — Ilosvay f has modified the method 
by substituting acetic acid for hydrochloric acid. The color 
is developed more rapidly and the gradation of color is more 
uniform. The process is carried out as above, except that 
10 c.c. of each of the reagents (p. 207), or 2 c.c. for 25 c.c. of 
the water, is used, and the colors are read after five minutes. 

Notes. — If the color obtained is more than that given by 
20 c.c. of the standard solution, as it may be in the case of 
water from bad wells and sewage effluents, the water should 
be diluted with nitrite-free water, 10 c.c. or even 1 c.c. being 
made up to 100 c.c. before adding the reagents, since colors 
above 20 c.c. are too deep for accurate comparison. 

* Defren: Tech. Quart.. 9 (189b). 238; Axson: loc. cit., 12(1899), 219. 
f Bull. Soc. Chim. [3], 2 (1889), 347. 



g6 air, water, and food. 

The reactions which take place consist first in the diazotiz- 
ing of the sulphanilic acid by the nitrite present in acid solu- 
tion, forming diazobenzenesulphonic anhydride. This reacts 
with the naphtylamine hydrochlorate, forming azo-a-amido- 
naphtylic parabenzol-sulphonic acid, which gives the pink 
color to the solution, the amount formed depending upon 
the amount of nitrite present. 

N N H 

I I I 

c c c 

/\ //\/ \ 

H— C C— H H— C C C— H 

II I I II I 

H— C C— H H— C C C— H 

\// \/\ // 

c c c 

I I I 

S0 3 H NH 2 H 

Determination of Nitrogen in the Form of Nitrates. 

— Directions. — Nitrogen in the fourth stage, that of nitrates, 
is next determined. In the case of ground-waters, measure 
two portions, one of 2 c.c. and one of 5 c.c, from the bottle, 
with a capillary pipette, into three-inch porcelain evaporating- 
dishes; for surface-waters, always low in nitrates, take 10 c.c. 
from the portion already decolorized in the determination of 
the nitrites. Place the dishes on the top of the water-bath 
and let their contents evaporate gently until one or two drops 
are left; then set them away in a place free from dust, that 
the remainder may evaporate spontaneously. Do not let 
them go quite to dryness on the bath. 

When the water is entirely evaporated, drop six drops of 
phenol-disulphonic acid directly upon the dry residue and 
rub it around with a glass rod to insure complete contact of 
the acid and the residue in the dish. Dilute the acid with 
7 c.c. of distilled water and add 3 c.c. of the alkali solution. 



WATER: ANALYTICAL METHODS. 97 

To prepare the standards, measure out the required amount 
of the standard nitrate solution (see Reagents, page 207) from 
the burette, add enough water to make the total volume 
10 c.c, and two or three drops of the alkali. One cubic 
centimeter of the standard solution contains 0.000001 gram 
N as nitrate. The comparison is best made in the small 
porcelain dishes. For high colors the liquids are compared 
in tubes similar to the Nessler tubes, but shorter. 

Notes. — It will be found that if 10 c.c. of a colored water 
be evaporated directly, the color obtained with the reagents 
will be much deeper as well as browner than that given by. 
the standards; hence the necessity for first decolorizing. 

Chlorine interferes with the accuracy of the method, but 
not to any extent when present in less than 20 parts per 
million. If the amount of chlorine be more than this, the 
evaporation should be made in vacuo over sulphuric acid. 
Nitrites do not interfere with the test. 

The reaction is generally considered to consist in the 
formation of picric acid. While this is not quantitatively 
true, it offers the best explanation of the changes that occur. 
Trinitrophenol (picric acid) is formed by the action of the 
nitrates in the cold, dry residue upon the phenol-disulphonic 
acid with which it is moistened: 

OH OH 

l A 

/ \ / ^ 

H— C C— SO3H NO— C C— NO, 

|| I +3HN0 3 = || I +2H,S0 4 

H— C C— H H— C C— H 

\// \ // + H 2 

C C 

S0 3 H NO, 

phenol-disulphonic acid. Picric acid. 



98 AIR, WATER, AND FOOD. 

The addition of an excess of caustic alkali converts the 
picric acid to the alkali picrate, which imparts an intense yel- 
low color to the liquid. The best color is obtained by the 
use of ammonia. 

Large quantities of nitrates in colorless water may be de- 
termined by reduction to ammonia by sodium amalgam, or 
by any reaction which yields nitrogen, this being measured 
as gas. 

Determination of the Carbonaceous Matter or " Oxy- 
gen Consumed." 

Rubers Hot Acid Method, 

Directions. — Measure ioo c.c. of the water into a 250-c.c 
flat-bottomed flask; add 8 c.c. of sulphuric acid (1:3) and 

about 10 c.c. of approximately potassium permanganate. 

Place the flask on wire gauze and heat it quickly to boiling. 
When the liquid begins to boil, introduce a small air-blast to 
prevent bumping and to avoid too great a rise of tempera- 
ture. Boil the solution for exactly five minutes; remove it 
from the flame; let it cool one minute, and add 10 c.c. of 

N 
exactly — — oxalic acid. Titrate with the permanganate to 

a faint permanent pink color. In order to find the exact 
value of the permanganate solution a blank determination 
must be carried through in precisely the same way, using 10a 
c.c. of water free from carbonaceous matter. 

Example. — In the blank determination, 10 c.c. oxalic acid 
requires 10.35 c - c - permanganate. Since 1 c.c. of the oxalic 
acid equals 0.00008 gram of oxygen, 1 c.c. permanganate 
equals 0.00007729 gram. 

Suppose 100 c.c. water + 10 c.c. oxalic acid required 
12.57 c.c. permanganate, then 12.57 — IO -35 = 2 - 22 c.c. per- 
manganate required by the water. 2.22 X .00007729 = 



water: analytical methods. 99 

.0001716 gram oxygen for 100 c.c. water = 1.716 parts per 
million. 

Notes. — For highly colored surface-waters 25 c.c. are 
taken and diluted to 100 c.c. with water free from organic 
matter; for sewages 10 c.c. are diluted in the same way. 

The oxygen given up by the permanganate combines 
with the carbon of the organic matter and perhaps to a cer- 
tain extent with the hydrogen, but not with the nitrogen. 
The amount of oxygen consumed bears some relation, there- 
fore, to the amount of organic carbon present in the water, 
but this relation certainly cannot be taken as a definite one 
in every case, the results varying even with the time of 
boiling. The method has its greatest value when it is 
used to compare waters of the same general character and 
having the same origin; for example, in making periodical 
tests of the purity of the effluent from a filter. Furthermore, 
in order that the results shall have this comparative value, 
it is absolutely necessary that the process shall always be 
carried out in exactly the same way, even to the minutest 
detail of quantity, time, and temperature. 

In some cases it may be found advantageous to heat the 
solution upon the water-bath for half an hour instead of boil- 
ing it for five minutes. 

Different kinds of organic matter behave differently with 
various oxidizing agents, so that a comparison of the results 
obtained with different oxidizing agents may throw light 
upon the character of the organic matter, as well as its 
amount.* In waters from the watersheds of eastern North 
America the color and the oxvgen consumed have a certain, 
though somewhat varying, relation. 

Determination of Chlorine. — The chlorine is deter- 
mined in natural waters by the method in general use; 

* Woodman: /. Am. Chem. Soc, 20 (i8g8), 497. 



100 AIR, WATER, AND FOOD. 

namely, titration with a solution of silver nitrate, using potas- 
sium chromate as an indicator. Since the exact change of 
color which constitutes the end-point will vary with the 
sensitiveness of the eyes of different observers to red, each 
person should standardize the silver nitrate solution for him- 
self. To do this, measure into a six-inch porcelain dish 25 
c.c. of distilled water; add 5 c.c. of sodium chloride solution 
from the burette and three drops of potassium chromate solu- 
tion. Titrate with the silver nitrate solution until the yellow 
color of the liquid assumes the faintest tinge of reddish 
brown. 

Directions. — Waters which are high in chlorine, i.e., which 
contain 20 or more parts per million, are titrated directly, 
using 25 c.c. either with or without the addition of 5 c.c. of 
the salt solution. Waters which are low in chlorine are con- 
centrated before titration, 250 c.c. being evaporated to 25 c.c. 
on the water-bath. Brown surface-waters should be decol- 
orized as follows: Pour into a 750-c.c. flat-bottomed flask 
about 500 c.c. of the water. Add 3 c.c. of the milk of 
alumina; shake and heat the water quickly to boiling on an 
iron plate. When the liquid comes to a full boil, at once 
remove the flask from the plate to avoid loss by evaporation. 
Place it in an inclined position to allow the alumina to settle. 
Decant off 250 c.c. of the colorless water into a six-inch dish 
for concentration to 25 c.c, using a flask calibrated for both 
the hot and the cold solution. Before making the titration, 
rub down the sides of the dish above the liquid with a small 
quantity of distilled water free from chlorine, using a clean 
feather. Rinsing alone will not always dissolve the chlo- 
rides which adhere to the sides of the dish. 

Notes. — For titration .by this method the solution must 
be as nearly neutral as possible. If the water is alkaline to 
any extent, it should be neutralized with dilute sulphuric acid, 



water: analytical methods. ioi 

using phenolphthalein as an indicator. The solution will 
then contain alkali only as bicarbonate, which does not 
interfere with the titration. Acid water must be made neu- 
tral by the addition of sodium carbonate. 

It is important that the process be carried out essentially 
as described, since it has been found that the results vary 
with the volume of solution in which the titration is made, 
the amount of chromate used, and the amount of precipitated 
silver chloride present.* A correction for volume can be 
made by means of the formula given by Hazen, but it is bet- 
ter to carry out the titration under similar conditions each 
time, and to use a volume of 25 c.c. rather than 100. 

Determination of the Residue on Evaporation and 
the Loss on Ignition. — Directions. — Ignite and weigh a 
platinum dish. Measure into it 100 c.c. of the water (200 
c.c. in the case of surface-waters), and evaporate to dryness 
on the water-bath. When the water is all evaporated heat 
the dish in the oven at the temperature of boiling water for 
two hours, then let it remain in a desiccator over sulphuric 
acid for several hours and weigh. f The increase in weight 
gives the " total solids " or " residue on evaporation/' If 
from a ground-water, save the residue for the determination 
of the iron. 

In the case of surface-waters the residue should be ignited 
and the loss on ignition noted. Heat the dish in a " radia- 
tor," which consists of another platinum dish enough larger 
to allow an air-space of about half an inch between the two 
dishes, the inner dish being supported by a triangle of plati- 
num wire. Over the inner dish is suspended a disk of 
platinum-foil to radiate back the heat into the dish. The 
larger platinum dish is heated to bright redness by a triple 

* Hazen: Am. Chem. Jour., II (i88q), 409. 

f In some laboratories it is the practice to dry at no° or 130 C. 



102 AIR, WATER, AND FOOD. 

gas-burner. Heat the dish in the radiator until the residue is 
white or nearly so. Note any blackening or charring of the 
residue and any peculiar " burnt odor " which may be given 
off. After the dish has cooled, slightly moisten the residue 
with a few drops of distilled water to secure weighing under 
the same conditions. Heat the residue in the oven for half an 
hour; cool in a desiccator and weigh. This gives the weight 
of " fixed solids," the difference being the " loss on ignition." 

Notes. — Before the introduction of modern methods of 
water-analysis the determination of " loss on ignition " was 
the only method for the estimation of organic matter in 
water. In order, however, that the determination shall pos- 
sess any real value, it is necessary to regulate carefully the heat 
during the ignition, so as to destroy the organic matter with- 
out decomposing calcium carbonate or volatilizing the alkali 
chlorides. 

This is what the use of the radiator is intended to accom- 
plish, and in the case of surface-waters, with low mineral con- 
tent and considerable organic matter, the method gives gen- 
erally satisfactory results. But in the case of ground-waters 
having little or no organic matter and high mineral content 
the loss is often very great on account of the decomposition 
of nitrates and chlorides of the alkaline earths and the loss of 
water of crystallization. In waters of this class the determi- 
nation of " loss on ignition " is, therefore, generally meaning- 
less, although an approximation to the amount of organic 
matter can be obtained by the addition of sodium carbonate to 
the water before evaporating to dryness. By this means the 
alkaline earths are precipitated as carbonates, the chlorine 
and nitric acid are held by an alkaline base, and there is no 
water of crystallization in the residue. Even with this modi- 
fication the loss is considerable when magnesium salts are 
present, owing to the loss of carbonic acid. 



water: analytical methods. 103 

The behavior on ignition is oftentimes significant. 
Swampy or peaty waters give a brownish residue on evapora- 
tion to dryness, which blackens or chars, and this black sub- 
stance burns off quite slowly. The odor of the charring is 
like that of charring wood or grain; sometimes sweetish, but 
not at all offensive. Waters much polluted by sewage blacken 
slightly; the black particles burn off quickly and the odor is 
disagreeable. Any observations on this point should be re- 
corded in the report (p. 120) under the heading " Change on 
Ignition." 

Determination of the Hardness. 

1. By Soap. — Clark's Method. 

Directions. — Measure 50 c.c. of water into a 200-c.c. clear 
glass-stoppered bottle and add the soap solution from the 
burette, two or three tenths of a cubic centimeter at a time, 
shaking well after each addition, until a lather is obtained 
which covers the entire surface of the liquid with the bottle 
lying on its side, and is permanent for five minutes. The 
number of parts of calcium carbonate corresponding to the 
volume of soap solution used is found in the table in Appen- 
dix A. 

This will give the total hardness. If it is desired to find 
the permanent hardness also, dilute 50 c.c. of the water to 
about 200 c.c. and boil down to 50 c.c. in a beaker, cool and 
determine the hardness as before. This will give the per- 
manent hardness, and the difference will be the temporary 
hardness. 

Notes. — When potassium or sodium soap is added to 
water containing calcium and magnesium salts, the soap is 
decomposed, and insoluble compounds with the fatty acids 
are formed. The importance of adding the soap in small quan- 
tities cannot be too strongly emphasized, especially in the 
presence of magnesium compounds. The presence of mag- 



104 AIR > WATER, AND FOOD. 

nesium salts will be recognized by the peculiar curdy appear- 
ance of the precipitate formed and by the occurrence of a 
false end-point, the lather lasting about three minutes when 
the titration is about half done. If much carbonic acid be 
liberated, it is better to follow Dr. Clark's original directions 
and remove it by suction. 

By reference to the table it will be observed that values 
are not given for more than 16 c.c. of the soap solution. If 
in any case the water under examination requires more than 
10 c.c. of the standard soap solution, a smaller portion of 
25 c.c, 10 c.c. or even 2 c.c, as the case may require, is meas- 
ured out and made up to a volume of 50 c.c. with recently 
distilled water. If the volume of soap used is always about 
7 c.c, this will keep the results comparable with each other, 
although the element of dilution introduces an error. Potable 
waters, in the eastern United States, at least, are rarely so 
high in mineral matter as to require excessive dilution. In 
the case of extremely hard waters, however, the acid 
method is to be preferred. Distilled water itself, containing 
no calcium salt whatever, requires the use of a considerable 
quantity of soap to produce a permanent lather. The cause 
for this seems to exist in the dissociation of the greater part 
of the soap at the extreme dilution to which it is subjected, 
and the slow accumulation of a sufficient quantity of undis- 
sociated soap to allow of the increase of surface tension to a 
point at which soap-bubbles will persist. 

By the temporary hardness of water is meant the hardness 
which is removed by boiling. It is due to the carbonates of 
calcium and magnesium held in solution by the carbonic acid 
in the water, probably in the form of bicarbonates. Perma- 
nent hardness is that which is not removed by boiling. It is 
caused by the presence of soluble salts of calcium and mag- 
nesium, not carbonates, but chlorides and sulphates princi- 
pally, held in solution by the solvent power of the water itself. 



WATER: ANALYTICAL METHODS. 105 



2. By Acid. — Hehner's Method. 

Directions. — For the determination of the temporary hard- 
ness or " alkalinity," measure ioo c.c. of the water into a 
bottle such as is used for the soap test, and add 2.5 c.c. of the 
erythrosine indicator and 5 c.c. of chloroform. Mix well by 

N 
shaking and add — sulphuric acid from the burette in small 
fe 50 r 

quantities, shaking thoroughly after each addition. The pink 

color gradually grows lighter until the addition of a drop or 

two of the acid causes it to disappear entirely. Each tenth 

of a cubic centimeter of acid used represents one part of 

CaCO s in 1,000,000. Make a correction for the indicator by 

carrying out a blank determination with distilled water. 

For the permanent hardness measure out 100 c.c. of the 

N 
water and add to it more than enough — sodium carbonate 

solution to decompose the calcium and magnesium chlorides, 
sulphates, and nitrates present. Generally 50 to 100 c.c. will 
be sufficient. Evaporate the mixture to dryness in a plati- 
num or nickel dish and dissolve the residue in a little recently 
boiled distilled water. Filter through a small filter and titrate 

N 
the filtrate and washings with — sulphuric acid, using ery- 
throsine as indicator. The difference between the number of 
cubic centimeters of sodium carbonate used and the acid re- 
quired for the residue will give the permanent hardness. 

Notes. — This method is especially useful for waters which 
require clarification by alumina and subsequent filtration. 
Lacmoid and phenacetolin can also be used in the determi- 
nation of the alkalinity, but they necessitate titration in a hot 
solution on account of their susceptibility to carbonic acid. 
The addition of chloroform when using erythrosine is to re- 



106 AIR, WATER, AND FOOD. 

move the non-ionized iodeosine molecule as rapidly as it is 
formed by the addition of acid. When it is thus removed the 
neutralization of the alkali is at once apparent and hence a 
sharp end-point is obtained.* 

If a water contains sodium or potassium carbonate there 
will not be any permanent hardness and hence more acid will 
be required for the filtrate than corresponds to the amount 
of sodium carbonate added. From the excess, the amount of 
sodium carbonate in the water may be determined. Any 
alkali carbonate present would be calculated as temporary 
hardness by the direct titration; hence it should be calcu- 
lated to calcium carbonate and subtracted from the results 
found by the direct titration. 

Determination of Iron.f — Directions. — Evaporate ioo or 
200 c.c. of the water to dryness in a platinum dish. (The 
weighed residue from the determination of total solids may 
be used if desired.) Treat the residue with 5 c.c. of hydro- 
chloric acid (1:1), being careful to carry the acid to the edge 
of the dish. In some cases it may be necessary to heat the 
dish gently on the water-bath in order to bring all the iron 
into solution. When all is dissolved with the exception of 
silica, rinse the solution into a 100-c.c. tube and make it up 
to about 50 c.c. with distilled water. Add a solution of po- 
tassium permanganate drop by drop until the solution re- 
mains pink for ten minutes. 

Meanwhile prepare a blank standard with 50 c.c. of dis- 
tilled water and about a cubic centimeter of hydrochloric 
acid. Add 15 c.c. of potassium sulphocyanide solution to 
the waters and to the blank standard. Add the standard iron 
solution, in small quantities, .02 c.c. if necessary, from a capil- 
lary pipette, mixing thoroughly by pouring the solution back 

* Ellms: J. Am. Chem. Soc, 21 (i8<p<p), 359. 
f Thomson: /. Chem. Soc, 67 {1885), 493. 



water: analytical methods. 107 

and forth from one tube to another after each addition, until 
the color of the standard matches that of the water. One 
cubic centimeter of the standard iron solution is equal to 
0,0001 gram of Fe. 

Notes. — In the case of some river-waters it will be found 
necessary to add a few cubic centimeters of hydrochloric acid 
to the water while evaporating, in order to facilitate the solu- 
tion of the iron. This should be done on a separate portion 
from that used for the determination of total solids. 

The colors should be matched immediately after adding 
the sulphocyanide, since the color fades appreciably on stand- 
ing. The highest standard should not contain more than 
3 c.c. of the iron solution, since the color then becomes too 
deep for accurate comparison. 

Determination of the Dissolved Oxygen. 

Method of L. W. Winkler* 

Collection of Samples. — The samples are collected in 
glass-stoppered bottles of known capacity, holding about 250 
cubic centimeters. When water is taken from a faucet the 
Dottle is filled by means of a tube which passes to the bottom 
of the bottle. A considerable amount of water is allowed to 
pass through the bottle and overflow at the top. It will be 
almost impossible to obtain duplicate samples unless the bot- 
tles are filled at the same time by means of a T tube, owing 
to variations in pressure in the pipes. 

In taking samples from a stream or pond, a stopper with 
two holes is used. A tube passing through one of these holes 
is sunk in the water to the desired depth, and the other is con- 
nected with a larger bottle of at least four times the capacity 
of the smaller one, and fitted in the same way. From the 

* Berichte, 21 {1888), 2843. 



108 AIR, WATER, AND FOOD. 

larger bottle the air is exhausted by the lungs or by an air- 
pump until it is nearly filled with water. Unless the determi- 
nation is to be made at once, the rubber stopper of the smaller 
bottle is quickly replaced by the glass stopper so that no 
air is left in the bottle. The temperature of the water at the 
time of sampling should be noted. This can be conveniently 
done at the depth at which the sample is taken, by means of 
a thermometer fitted by a doubly perforated stopper to a bot- 
tle of about 500 c.c. capacity which has been filled with some 
of the water and then lowered to the desired depth. An in- 
strument capable of giving more accurate readings is the 
" thermophone " of Whipple and Warren.* 

The Determination. — Remove the stopper and add 2 c.c. 
of manganous sulphate solution with a pipette having a long^ 
capillary point reaching to the bottom of the bottle, and in 
the same way add 2 c.c. of a solution of sodium hydroxide 
and potassium iodide. Insert the glass stopper, leaving no 
bubbles of air, and mix the contents of the bottle. Allow 
the precipitate to settle and add 2 c.c. of strong hydrochloric 
acid with another pipette. When the precipitate is nearly all 
dissolved, rinse out the contents of the bottle into a flask and. 

N 
titrate the liberated iodine with approximately sodium 

thiosulphate until the color becomes a faint yellow. Then 
add starch solution and titrate to the disappearance of the 
blue color. The first end-point should be taken, as the color 
will return on account of the reducing action of the organic 
matter present. Determine the exact normality of the thio- 
sulphate solution by standardizing it against a solution of 
potassium bichromate (1 c.c. equals 0.001 gram iodine) as. 
directed on page 176. 

* J. JV. E. Water Works Assoc, g (i£<pj), 203. 



water: analytical methods. 109 

N 
Calculation of the Results. — 1 c.c- sodium thiosulphate 

= 0.055825 c.c. oxygen at o° and 760 mm. (This value would 
ordinarily be corrected for the barometric pressure, but the 
correction falls within the limits of experimental error.) Find 
the volume of oxygen by substitution in the following for- 
mula: 

n X 0.055825 X 1000 . _ 

A = — — =c.c. oxygen in ioooc.c. of water, 

N 

where n = number of c.c. of exact thiosulphate, and v == 

100 

the volume of the bottle minus 4 c.c. (lost by addition of rea- 
gents). The results are reported in " per cent, of saturation," 
which is found by dividing A by the number of c.c. of oxygen 
taken up by 1000 c.c. of water when saturated at the given 
temperature. (See Winkler's table, Appendix A.) 

1ST 
For example, 30.4 c.c. ^c7 thiosulphate were used to 

titrate the iodine liberated by the oxygen in 265.5 c - c - °f the 
water. Temperature of sample was 9 C. Then 

_ 30.4 X 0.055825 X 1000 
265.5-4 

= 6.491 c.c. oxygen in 1000 c.c. of water. 

From the table, 1000 c.c. water at g° C. dissolves 8.063 

6.491 
c.c. oxygen. Hence the " per cent, of saturation " = ~ — -r- 

= 80.50 per cent. 

Notes. — This determination is a good illustration of an 
indirect volumetric process. A precipitate of manganous 
hydroxide is formed in the bottle by the reaction of the 
manganous sulphate and the sodium hydroxide. This imme- 
diately combines with the oxygen in the water to form a cer- 



IIO AIR, WATER, AND FOOD. 

tain amount of manganic hydroxide. The hydrochloric acid 
which is added reacts with the manganic hydroxide to form 
chlorine, which in turn liberates iodine from the potassium 
iodide, the amount thus set free depending primarily upon 
the quantity of oxygen dissolved in the water. The presence 
of considerable amounts of organic matter or of nitrites in- 
troduces an error. In such cases the method must be modified 
or a correction made. Details of the method used in such 
cases are given in the paper by Winkler previously cited. 

A correction is made for the volume of the reagents 
added, but if the precipitated hydroxides had settled before 
the acid was added, no allowance should be made for the 
amount of acid, since the water it displaces contains neither 
oxygen nor iodine. 

If water is collected in the ordinary way and transferred 
to the apparatus by pouring, there will inevitably be an ab- 
sorption of oxygen unless the water is already saturated. 
Thus a process which gives excellent results when the water 
is nearly or quite saturated may fail entirely to give accurate 
results when the dissolved oxygen is low or absent. The 
water may be supersaturated with oxygen, in which case the 
per cent, of saturation may be more than one hundred.* 

Determinations of dissolved oxygen in ponds and streams 
are best made on the spot. The very simple apparatus re- 
quired for the Winkler process can be packed in small space, 
and the entire determination requires only a few minutes. 
The absorption of the oxygen by the manganous hydroxide 
is complete almost at once, and it is unnecessary to allow it 
to settle for a long time before adding the acid. The titra- 
tion can be made with a small burette or pipette with accurate 
results. 

* Gill: Tech. Quart., 5 (1892), 250. 



WATER: ANALYTICAL METHODS. Ill 

Determination of Free Carbonic Acid. — Directions. — 
Measure ioo c.c. of water into a flask, add 10 drops of 

N 
phenolphthalein solution and titrate with — sodium car- 
bonate solution until a faint permanent pink color is pro- 
duced. To obtain the exact value make a second titration, 
running in the sodium carbonate rapidly until near the end 
and then drop by drop until the exact point is reached. The 
pink color will disappear rather slowly near the end. One 
cubic centimeter of the sodium carbonate solution = 0.44 
milligram of C0 2 . 

Note. — The reaction consists in the formation of acid so- 
dium carbonate: 

Na a C0 3 + H a O + CO, = 2NaHC0 3 

The acid carbonate does not give a pink color with phenolph- 
thalein. Sodium hydroxide can also be used for the titration, 
but the sodium carbonate solution is preferable. 

Determination of the Color. — The amount of color is 
generally determined by direct comparison of the water with 
some definite standard of color. Various standards of color 
have been proposed, the objection to most of them being that 
they are not sufficiently general in their application, being 
adapted only for the color of some particular class of waters. 

Nesslerized Ammonia Standards. — The yellowish-brown 
tint of the surface-waters of the Atlantic watershed corre- 
sponds, except in the lowest grades, very closely to that of 
nesslerized ammonia, so that the standards for reading am- 
monia can be used also for the determination of the color. 
The comparison is made in the same kind of 50-c.c. tubes 
that are used for the ammonia determinations, but the tubes 
used for this purpose are kept separate from those used for 
the ammonia, since the least amount of alkali remaining in 



112 AIR, WATER, AND FOOD. 

a tube (from imperfect washing, for instance) alters the color 
of the water. The scale used corresponds quite closely with 
the amount of the standard ammonium chloride solution in 
the standards. Thus a color of i.o is nearly the same as that 
produced by the nesslerization of i c.c. of the standard 
ammonia; o.i is about the color produced with o.i c.c. of 
the ammonia solution. In the higher grades of color, above 
i.o or 2.0, the tint varies considerably from that of the nes- 
slerized ammonia, and the degree of color is then better de- 
termined in wider tubes and in less depth. 

The degree of correspondence of the ammonia standards 
with the natural waters is dependant largely upon the sensi- 
tiveness of the Nessler's reagent, a solution which is so sen- 
sitive as to precipitate in two hours, matching the colors more 
closely than one which will remain for twenty-four hours. 
This is perhaps due to the reddish tinge given to the solution 
by the incipient precipitation of the mercuric iodide. 

Natural Water Standards. — To avoid these variations in 
color, standards made from dark-colored water from swamps 
by various degrees of dilution, and verified by direct com- 
parison with suitably prepared nesslerized ammonia stand- 
ards, are used. They have the same hue as the waters to be 
matched, as well as a degree of turbidity which corresponds 
well with that of surface-waters; once prepared, they will 
keep for a fairly long time if protected from the light and 
from the dust. These are the standards that are in use in this 
laboratory. 

Platinum Standards. — For ground-waters, which have 
only very little color and considerable hardness, and for fil- 
tered waters, the platinum color standards are convenient.* 
According to this scale, the color of a water is the amount of 

* Hazen: Am. Chem. J., 14 {18Q2), 300. 



water: analytical methods. 113 

platinum in parts per ten thousand, which, together with 
enough cobalt to match the tint, must be dissolved to pro- 
duce an equal color in distilled water. In practice, a stand- 
ard having a color of 5.00 is prepared by dissolving 1.246 
grams of potassium platinic chloride (equivalent to .5 gram 
platinum), 1.000 gram of cobalt chloride (equivalent to .25 
gram cobalt), and 100 c.c. of strong hydrochloric acid in dis- 
tilled water and diluting to one liter. 

Dilute standards for use are made by diluting varying 
amounts of this standard to 50 c.c. with distilled water. Thus, 
by diluting 1 c.c, 2 c.c, and 3 c.c. to 50 c.c, colors of 0.1, 0.2, 
and 0.3 are obtained. It is claimed that the platinum stand- 
ards are permanent if protected from the dust. 

Iodine Standards. — A standard for color which could be 
made up at the moment when wanted and without the use of 
costly apparatus would be a desideratum. Experiments made 
in this laboratory indicate that an aqueous solution containing 
a definite weight of iodine offers the best solution of the prob- 
lem. Owing, however, to the volatility of iodine even in 
dilute aqueous solution it is better to liberate it directly in 
the comparison-tube itself. For this the following solutions 
are required: Potassium iodide, 0.1 gram per liter; potas- 
sium bichromate, 0.09 gram per liter; picric acid, 0.2 gram 
per liter. 

For a color of 5.0, 50 c.c each of the iodide and of the 
bichromate solutions are used; for lower colors proportional 
amounts are taken and diluted to 100 c.c. with distilled water. 
To each tube is added 1 c.c of the picric acid solution, and 
just before the colors are to be matched add 2 c.c. of strong 
sulphuric acid. The color develops, as in the case of nessler- 
ized ammonia, within ten minutes and can be relied upon 
for about half an hour. A very slight milkiness aids in match- 
ing the color; a great hindrance to the use of metallic solu- 



114 AIR > WATER, AND FOOD. 

tions being their clearness or brightness as compared with 
natural waters. 

The comparison-tubes which give the most satisfactory 
results with colors from 5.0 to 0.5 on the natural water scale 
are 15 / 16 inch wide and 9V4 inches high to the 100-c.c. mark, 
For lower colors, narrower tubes, n /i6 i ncn diameter and the 
same depth, give closer readings. 

Determination of the Odor. — Cold. — Shake violently 
the sample in one of the large collecting-bottles when it is 
about half or two-thirds full, then remove the stopper and 
quickly put the nose to the mouth of the bottle. Note the 
character and degree of intensity of the odor, if any. An 
odor can often be detected in this way which would be en- 
tirely inappreciable if the water were poured into a tumbler. 

Hot. — Pour into a beaker about five inches high enough 
water to one-third fill it. Cover the beaker with a well-fitting 
watch-glass and place it on an iron plate which has been pre- 
viously heated, so that the water shall quickly come to a boiL 
When the air-bubbles have all been driven off and the water 
is about to boil, take the beaker from the plate and allow it 
to cool for about five minutes. Then shake it with a rotary 
movement, slip the watch-glass to one side and put the nose 
into the beaker. Note the odor as before. The odor may or 
may not be the same as that of the water when cold; it can 
be perceived, as a rule, for only an instant. 

Notes. — It is inevitable that a certain personal equation 
should influence this test. Each laboratory will have its own 
standards for routine work, but a certain familiarity with the 
more common odors will tend to allay public anxiety and to 
aid in a more watchful habit on the part of consumers. Good 
ground-waters do not give distinct odors unless they are de- 
rived from clayey soil, but the odor often betrays a contami- 
nated well more surely than any other test. Surface-waters 



water: analytical methods. 115 

will nearly always yield a characteristic odor. This odor may 
be due to the organic matter contained in the water, or to 
the presence of minute plants or animal organisms. 

Among the odors which are frequently met are the 
" earthy," " vegetable," " musty," " mouldy," " disagree- 
able," and " offensive." The " earthy " odor is that of 
freshly turned clayey soil. " Vegetable " is the odor of 
many normal colored surface-waters; it may be described 
as swampy or marshy, pond-like, and is often strengthened 
by heating. " Musty " can be likened to the odor of damp 
straw from stables; it is fairly characteristic of sewage con- 
tamination, and by the trained observer is distinctly distin- 
guishable from the mouldy odor. " Mouldy " is the odor of 
upturned garden or forest mould, or of a moist hot-house; 
it is somewhat allied to the earthy odor. " Disagreeable " 
is a term which is capable of wide variation among different 
observers. It may include certain characteristic odors which 
are peculiar to the growth or decay of certain organisms, as 
the " pigpen " odor of Anabcena, the " fishy " or " cucum- 
ber " odor of Synura, etc. The term " offensive " is generally 
reserved for the sewages. These terms can be taken only as 
broad illustrations of the character of the particular odor, 
since the odor will very likely be described by different per- 
sons in different ways, and each laboratory will have its own 
characterization. The odor which often accompanies an 
abundant development of diatoms is a good illustration of 
this. It will be called by various inexperienced observers 
offensive, rotten, fishy, geranium-like, aromatic, in one and 
the same sample of water. 

The terms generally used to signify the degree of inten- 
sity of the odor are " very faint," " faint," " distinct," and 
" decided." The exact value to be placed on each of these 
terms will, as a matter of course, vary with the individual 



Il6 AIR, WATER, AND FOOD. 

analyst, but in a general way it may be said that the " very 
faint " odor is one that would not be detected except by the 
trained observer; the " faint " odor would be recognized by 
the ordinary consumer if his attention were called to it; the 
" distinct " odor is one that would be readily noticed by the 
average consumer, but would not interfere with the use of 
the water; while the " decided " odor is one which would, in 
all probability, render the use of the water unpleasant. 

Biological Examination — The close relation of the odor 
to the living fauna and flora of the water makes it desirable 
that the chemist shall be able to recognize the more common 
forms of water plants and animals even if he makes no pre- 
tensions to a knowledge of cryptogamic botany or of zo- 
ology. Therefore a microscope and a concentration appara- 
tus should be in every water-laboratory. A full description 
will be found in Whipple.* 

The bacteriological examination belongs to the expert 
rather than to the student, certainly in the present state of 
our knowledge of the lower organisms. It may be desirable 
for the student to be familiar with the simpler methods of 
plate and tube culture, and the water-works laboratory 
should, as in the above case, be provided with means for plain 
number counts, and directions for avoiding errors due to 
variations in temperature, time of culture, etc. A book to be 
recommended is Frankland's " Micro-organisms in Water." 

Determination of the Turbidity and Sediment. — The 
suspended matter remaining in the water after it has rested 
quietly in the collecting-bottle for twelve hours, or more, is 
called its turbidity, and that which has settled to the bottom 
of the bottle, its sediment. 

Good ground-waters are often entirely free from turbidity 

* " Microscopy of Drinking-water." N. Y., Wiley, 18Q9. 



water: analytical methods. 117 

and sediment, the suspended matters having been filtered out 
during the subterranean passage of the water, but this is 
rarely true of surface-waters. The turbidity is various in 
character and amount, sometimes milky from clay or ferrous 
iron in solution; usually it consists of fine particles, generally 
living algae or infusoria. These often collect on the side 
toward or from the light, and a practised eye can, not infre- 
quently, recognize their forms. Some of the lower animal 
forms can also be seen by the naked eye, and the larger En- 
tomostraca are quite noticeable in many waters. 

The sediment may be earthy or flocculent; in the latter 
case it is generally debris of organic matter of various kinds. 
The degree of turbidity is expressed by the terms " very 
slight," " slight," " distinct," and " decided," and the degree 
of sediment by " very slight," " slight," " considerable," and 
" heavy." These determinations, again, are of value only to 
the routine worker, and for him there are various methods in 
use. The papers of Parmelee and Ellms * and of Whipple 
and Jackson f should be consulted for a description of these. 

Determination of Alum. — On account of the use of alum 
or aluminum sulphate as a coagulant in the filtration of water, 
a determination of alumina in the effluent water is often nec- 
essary. This may be readily made by the logwood test.J 

Directions. — Dissolve about 0.1 gram pure haematoxylin 
in 25 c.c. water; this solution will keep for two weeks and 
works best after being made several hours. To 50 c.c. of the 
water, placed in a four-inch porcelain dish, add two drops of 
the haematoxylin solution, allow the solution to stand for 
one or two minutes, then add a drop of 20 per cent, acetic 
acid. The standards are prepared at the same time, using 
50 c.c. of distilled water and the required amount of a stand- 

* Tech. Quart., 12 (i8gg), 145. f Ibid., 283. 
% E. H. Richards: Tech. Quart., 4 (189 1), 194. 



Il8 AIR, WATER, AND FOOD. 

ard alum solution. The comparison must be made imme- 
diately, since the color fades on standing. In this way the 
presence of one part of aluminum sulphate in five million can 
be determined directly in the water and with ease. 

Logwood itself can be used, but the test is not so delicate 
as with the hsematoxylin. Boil 5 grams rasped logwood re- 
peatedly with 50 c.c. of water; reject the first four decoctions, 
saving the fifth for use. This solution is used in the same 
way as the hsematoxylin solution, but the fainter colors are 
not so easily seen, on account of the greater color of the log- 
wood solution itself. The logwood solution must be freshly 
prepared each time. It will work satisfactorily only for about 
two hours. 

Notes. — This test will show the presence of all soluble salts 
of aluminum which enter into combination with the coloring 
matter of the logwood to form a " lake." 

The alkalies and alkaline earths give a purplish color with 
logwood extract, hence the test for alum can be made only in- 
acid solution. 

Determination of Lead.— Lead in the minute quantities 
in which it ordinarily occurs in water is best estimated by 
comparing the color of the sulphide with standards. 

Directions. — If the water is colorless, acidify the clear solu- 
tion, concentrated if need be, with two or three drops of 
acetic acid, and pass in hydrogen sulphide to saturation. If 
a color is produced, compare it in a 100-c.c. tube with the 
color given by varying quantities of a standard lead solution.. 

If the water is too highly colored to estimate the lead di- 
rectly, evaporate three or four liters in a porcelain dish to 
about 25 ex., add 10 c.c. of ammonium chloride solution and 
a considerable excess of strong ammonia. Then add hydro- 
gen sulphide water and allow the dish to stand some hours. 
Boil the contents of the dish for a few moments to expel the 



water: analytical methods. 119 

excess of hydrogen sulphide, and filter. The precipitate con- 
tains all the lead, iron, and suspended organic matter, also 
copper and zinc if present, while the soluble color goes into 
the filtrate. Wash once with hot water, transfer the filter to 
the original dish, ajid dissolve the sulphides by boiling with 
dilute nitric acid (1 part acid, sp. gr. 1.2, to 5 parts water). 
Filter and wash; evaporate to 10-15 c.c, cool, add 5 c.c. con- 
centrated sulphuric acid and evaporate until copious fumes 
are given off. Then, if the original water contained less than 
0.25 part iron per million, add acetic acid and ammonia, boil, 
filter, and read the amount of lead in the alkaline filtrate, 
making the standards (page in) also alkaline with ammonia. 

If the water contained over .25 part iron, wash the lead 
sulphate into a beaker with alcohol and water, and let it set- 
tle overnight. Filter, wash free from iron with 50 per cent, 
alcohol, dissolve the precipitate by boiling with ammonium 
acetate, filter, and determine the lead as above. 

Note. — If more than .25 part of iron is present, some of 
the lead will be held by the precipitated ferric hydroxide; and 
if 25 parts are present, all of the lead may be lost in this way; 
hence the modification of the method in the presence of con- 
siderable quantities of iron.* 

When copper is also present it is detected by the blue 
color given to the ammoniacal filtrate from the iron precipi- 
tation. 

Statement of Results — In reporting water analyses the 
results are best expressed in milligrams per liter, which for 
the majority of waters is equivalent to " parts per million." 
Occasionally it may be desirable to express the results in 
" grains per gallon." Parts per million may be converted into 
grains per U. S. gallon by multiplying by 0.058. For con- 

* Ann. Rep. State Bd. Health, Mass., 1898, 577. 



120 



AIR, WATER, AND FOOD. 



venience the results should be arranged in tabular form, such 
an arrangement being suggested below: 

SANITARY WATER-ANALYSIS. 
(Parts per 1,000,000.) 





Date. 


Physical. 


Residue on Evaporation. 


No. 


Color. 


Turb. 


Sed. 


Odor. 


Total. 


Loss. 


Fixed. 


Change 




Cold. 


Hot. 


Ignition. 


121 


3- 9 -'oo 


•50 
0.0 
0.0 


Dec. 

None 


Cons. 

None 


None 


F. Veg. 
None 


42.5 

64.0 

9740.0 


12.5 


30.0 


| Slight 
1 black 


123 











Nitrogen as 




No. 


Total 
Organic. 


Alb. Ammonia. 


Free Am. 


Nitrite. 


Nitrate. 


Ox. 

Cons. 




Total. 


Sol. 


Susp. 




121 


.598 


.306 
.014 
.032 


.170 


.136 


.056 
.000 

.560 


.003 
.000 
.003 


.220 
1.40 


4.83 

.41 

3-23 


123 















Hardness 


Chlorine. 


Iron. 


Biological (per c.c.) 


No. 


Bac. 


Plants. 






Diatoms. 


Cyano- 
phycese. 


Algae. 


Animals. 




20.0 

23.0 

560.0 


1.8 
6.3 

1198.0 






■ 








229 




.01 

.46 




123 























No. 121 is from a pond; 122 from a spring; 123 from an artesian well. 



CHAPTER VIII. 

FOOD IN RELATION TO HUMAN LIFE: COMPOSITION, SOURCES, 

DIETARIES. 

Paracelsus (1493-1541) taught that " the object of 
chemistry is not to make gold, but to prepare medicines." 
Van Helmont (1577) recognized water as a chief constituent 
of all living matter. Sylvius (1614) taught that combustion 
and respiration were precisely similar phenomena. The mod- 
ern revival of chemistry has been largely due to efforts to 
preserve health. These efforts are turned more and more to 
the attainment of a high degree of daily efficiency instead of 
toward curing already established disease. Life itself is con- 
ditioned on the food-supply. Wholesome food is a necessity 
for productive life. Man can and does exist on very unsuit- 
able, even more or less poisonous, food, but it is merely ex- 
istence and not effective life. This is true not only of the 
wage-earner, but of the business-man, the professional man, 
the scholar. To be well, to be able to do a day's work, is 
man's birthright. Nevertheless a too large proportion of the 
American people sells this most valuable possession for a 
mess of pottage which pleases the palate for three minutes 
and weights the digestive organs for three hours. With no 
other known source of bodily energy, the student cannot 
afford to use up the capital in his bank lest he find the account 
overdrawn before middle age. With no hope of entirely ban- 
ishing evil microbes from the haunts of men, it behooves each 
one to so nourish his body that the enemy can find no point 
of attack. 



122 AIR, WATER, AND FOOD. 

The watchword of the State is prevention of disease; that 
of the individual is personal resistance. The economic and 
social conditions of daily life have reached such a stage of 
development as to make a closer study of food-materials, for 
which half the cost of living is spent, not only desirable but 
imperative. With the products of the world exposed in our 
markets, the restraints of a restricted choice, as well as in- 
herited instincts or traditions, lose their force. The buyer, 
unless he has actual knowledge to guide him, is swayed by 
the caprices of the moment or the condition of his purse, and 
often fails to secure adequate return in nutritive value for the 
money paid. 

The fact that so much manipulated material is put upon 
the market renders this choice of food doubly difficult, since 
the appearance of the original article is often entirely lost, 
and to city-bred buyers even the natural product conveys 
little idea of its money value. It therefore seems necessary that 
an elementary knowledge of the proximate composition and 
food value of the more common edible substances should be 
recognized as an essential part of education. Chemistry is 
now found in the curricula of nearly all institutions devoted to 
higher education, so that it is possible, as it was not ten or 
twenty years since, to bring to students both the theoretical 
and the practical bearing of a study of food-materials in an 
instructive and practical manner. No branch of Sanitary 
Chemistry can yield more far-reaching results in the welfare 
of the community, since the more widely this knowledge of 
the composition of foodstuffs is disseminated the less danger 
to health and purse from the sophistications of unscrupulous 
dealers. 

True, the subject is not yet in that condition in which 
there is nothing more to learn. It cannot be taught in a 
dogmatic manner. No hard-and-fast rules can be given 



FOOD IN RELATION TO HUMAN LIFE. 1 23 

either as to the quantity or the quality of the daily diet, but 
enough is known to enable us to make life of more value, to 
lessen the suffering due to disease, and, consequently, to 
lower the death-rate and increase the productive power of the 
community. 

Attention must be called to this relation of food to health 
if the delicacy of constitution due to civilized habits is to be 
overcome and the lives of useful citizens prolonged. Men 
otherwise sane are most reckless where food is concerned. 
Even noted authorities on sanitation have succumbed to dis- 
ease because the proper balance of nutrition and exercise 
was neglected. The physician is to a great extent powerless, 
for if his advice displeases he is dismissed. It remains for 
the school to educate the young student, and as usual the 
higher education must begin the work and the college pro- 
fessor must set the example of a living plain enough to be 
consistent with clear thinking. There need be no apology, 
therefore, for the introduction of such a " practical " subject 
into any college curriculum. There is plenty of theory be- 
hind it and much educational value in both methods and rea- 
soning. 

Definition of Food. — Food is that which builds up the body 
and furnishes energy for its activities: that which brings 
within reach of the living cells which form the tissues the ele- 
ments which they need for life and growth. Only such avail- 
able substances can be called food, no matter what their 
chemical composition may be. Soft coal contains carbon and 
hydrogen and is food for the furnace, but is not available for 
the animal body. 

If for any reason a portion of the digestive tract is dis- 
eased, substances which under normal conditions would be 
food may not be nutritious. 

The nutritive value of a food depends upon the quantity of 



124 AIR > WATER, AND FOOD. 

its ingredients which under normal conditions may be useful 
to the human organism. The term is not confined to any 
one class of food principles, as is commonly the case in news- 
paper articles, in which it is often stated, for example, that 
white flour and rice have very little nutritive value. 

We determine what chemical elements enter into the 
composition of the body by an analysis of the various organs 
and tissues. We learn what combinations of these ele- 
ments serve as food by determining those present in mother's 
milk and in foodstuffs which experience has proved to fur- 
nish perfect nutrition. From these studies it is apparent that 
about fifteen chemical elements are constant constituents of 
the human body; that about a thousand natural products are 
known to have food value; that of these, one hundred are of 
world-wide importance (see table, page 130), and that ten of 
them form nine-tenths of the food of the world. 

Food Principles. — While the foodstuffs present great vari- 
ety, the food principles may be grouped under four headings; 
viz., nitrogenous substances or proteids, fats, carbohydrates, 
and mineral salts. Each group contains many members with 
minor but often essential differences. To make these sub- 
stances available, there is needed an ample supply of air and 
of water, — of water for solution and circulation, of air for the 
oxygen needed to liberate the stored energy of the food in the 
place where it will accomplish its purpose. 

Nitrogenous Substances. — Since, in some way as yet un- 
known to us, nitrogen is essential to living matter, such sub- 
stances as contain this element in an available form are of the 
first importance. Some, as albumen, are so closely allied to 
human protoplasm that probably they need only to be dis- 
solved to be at once assimilated. Others, as gluten and sim- 
ilar vegetable products, undergo a greater change; while still 
others, as gelatine, have a less profound but marked effect in 



FOOD IN RELATION TO HUMAN LIFE. 12 5 

protecting the tissues from waste. Still other nitrogenous 
substances, as the alkaloids, seem to affect the nerve-tissues 
for good or ill. 

The enzymes, " ferments," in part, of the older nomencla- 
ture, are also highly nitrogenous substances present in some 
form in nearly all foodstuffs of natural origin. The nearer 
the composition of the food approaches that of the protoplas- 
mic proteid, presumably the greater its food value, since each 
cleavage, each hydrolysis, each step in the breaking down of 
the highly complex molecule, consisting of hundreds of atoms, 
is supposed to liberate the stored energy. Therefore it is not a 
matter of indifference in what form this essential is taken. So 
little is known, however, with scientific accuracy that stu- 
dents will find a fruitful field of research along these lines of 
investigation. Also together with this element, nitrogen, go 
others, in small quantity to be sure, but evidently of great 
value. Such are sulphur, iron, phosphorus. One difference 
between the several groups of proteids is seen in this com- 
bination with the metallic elements which seems to carry with 
it certain effects. Until greater progress has been made in 
determining the availability in the organism of the various 
known substances, we must be content with a wide margin 
in the calculated quantities necessary for the daily efficiency, 
except in the very few instances of nearly pure substances, as 
white of egg. It is evident also that the manner of prepara- 
tion and the kind of mixtures used in food will affect most 
profoundly so unstable and complex a class of substances, 
and that only very general conclusions can be drawn from the 
work done as yet. One thing is certain, that the body cannot 
take nitrogen from that which does not contain it. There- 
fore a certain quantity of highly nitrogenous food should form 
a portion of the daily supply. It is usually held that the body 
seems to be sufficiently nourished when the food contains 



126 AIR, WATER, AND FOOD. 

an amount of digestible proteid equivalent to about ioo 
grams of dry albumen per day for the average adult, although 
recent work has shown that this figure is probably too high. 
An excess appears to have a stimulating effect and overloads 
the system with the waste, since the end-products are not 
purely mineralized substances, as are carbon dioxide and 
water from the carbohydrates, but are compounds of an or- 
ganic nature, as creatin, urea, and uric acid, which have 
deleterious effects when accumulated in the system. A de- 
ficiency of nitrogen is made good, to a limited extent, by the 
protective agency of the other foodstuffs which offer them- 
selves for all the offices except the final one of tissue-building. 
Fats. — For this protective action, as well as for many other 
purposes, the fats are most valuable, and if they occur in about 
the same proportion as do the nitrogenous elements, the 
needs of the organism seem to be well met. Thus, in mother's 
milk, in eggs, and in meat from active animals these two are 
in nearly equal proportions, while in the cereals the fat is less; 
in nuts and in meat from fattened animals, as a rule, it is 
higher than the nitrogen. Little is known as to the varying 
food value of these fats from different sources. Certain 
physical conditions of solidity, melting-point, etc., seem to 
have more influence than mere chemical composition. What- 
ever the source, it is certain that the stored-up energy which 
is to serve the organism in cases of loss of income from any 
cause is in the form of fat, a form which is not subject to the 
action of agents which so readily decompose proteids and 
carbohydrates and yet is readily converted into available food 
whenever called for. That it is not absolutely necessary that 
the food should contain fat as such seems to be proved by 
experiment, but from the fact that all nearly natural food- 
substances do contain it, and that it appears to be more 
economical of human energy to take it from these foods than 



FOOD IN RELATION TO HUMAN LIFE. 1 27 

to manufacture it from the proteids and carbohydrates, we 
may safely assume fat to be an essential of the human dietary. 

That the equality in amount of fat with nitrogenous com- 
pounds is not essential is proved by the fact that the strong 
draft animals, as horses and oxen, take food in which the per 
cent, of fat is not more than half as much as of proteid; never- 
theless it is present in the food of all animals and doubtless, 
in its turn, is protected by an excess of the third class of 
foodstuffs, the carbohydrates, characteristic of the vegetable 
kingdom — a class which in the final decomposition yield clean 
volatile products, water and carbon dioxide, and which, there- 
fore, do not clog the system so readily as do urea and other 
wastes. 

Carbohydrates. — The number of more or less well-defined 
substances under this head is legion: starches from scores 
of plants, sugars from as many more, gums, pectins, and 
dextrins, all with a certain food value, dependent prob- 
ably upon the utilization of the various mixtures with 
which they are taken into the alimentary canal. These 
foodstuffs are very liable to " fermentation," that is, to an 
acid decomposition which prevents their absorption by 
the delicate lining of the walls of the intestines and which 
causes digestive disturbance. The sugars, which are very 
soluble, and therefore liable to be present in excess, are es- 
pecially subject to this change. This class of food-substances 
is found in the diet of civilized man, free to choose, in an 
amount about equal to the sum of the other two classes, with 
a tendency to less rather than more. It may be said that 
sugar and fat increase over starch in the diet of a people of 
unrestricted choice, but it is not certain that the qualities of 
body which make for hardihood and resistance to disease 
are correspondingly increased. There is, indeed, much evi- 
dence to show that power of digesting vegetable foods indi- 
cates a general well-being of body conducive to long life. A 



12 8 AIR, WATER, AND FOOD. 

ready adaptation renders possible the changes of habitat re- 
quired by civilization. Unless one is to be confined to a nar- 
row range it is wise to cultivate a strength of digestion as 
well as a strength of muscle, and for the best brain power we 
believe it to be more essential. 

Mineral Salts. — The fourth class, mineral salts, comes into 
the food largely from the vegetable substances eaten, for in 
these the union is an organic one readily assimilated. As we 
have seen, certain elements go with the nitrogenous portion, 
as, for example, in gluten and its congeners are found sul- 
phur and phosphorus. Potassium, found in barley, is a con- 
stant constituent of protoplasm, while sodium is found in 
blood-serum. A lack of vegetable foods seems to impoverish 
the blood-corpuscles. For children, a deficiency in lime 
causes serious disease. Sugar, olive-oil, corn-starch, and 
other prepared food-substances cannot take the place of 
asparagus, cabbage, carrots, etc. 

Heat of Combustion. — Until a more definite knowledge 
of the processes of metabolism (the transformations of matter 
and energy in the animal organism) is obtained the potential 
energy of food is calculated in terms of mechanical work — 
expressed in heat-units or calories. 

One Calorie (1000 calories) is that amount of heat which 
is required to raise the temperature of one kilogram of water 
one degree centigrade, and if expressed in terms of mechani- 
cal work would enable one ton to be lifted 1.53 feet. For 
example: one gram of fat burned under a steam-boiler would 
yield, if the heat were completely utilized, 9.3 Calories, and 
raise one ton 14.2 feet; 100 grams would yield 930 Calories 
and raise one ton 1423 feet. 

One gram of proteid or of carbohydrate is usually 
reckoned as yielding only 4.1 Calories. 480 grams would 
yield 1968 Calories and raise one ton 301 1 feet. A day's 
ration is frequently estimated as 100 grams fat + 480 grams 



FOOD IN RELATION TO HUMAN LIFE. 129 

of proteid and carbohydrates, and if completely converted 
into mechanical work would yield that amount of energy 
which would suffice to raise 156 pounds (taken as the weight 
of the average human body) 56,755 feet. But a portion of 
this energy is used up in chemical processes, a portion in 
physical changes, and a portion is undoubtedly wasted; a 
portion of the food may be of no use or even detrimental to 
the body, so that not more than one-third of this work can 
be counted as available. Hence 18,918 feet may be counted 
as a theoretical day's work in mountain-climbing. 

The fact remains, however, that all experiments yet made 
go to show that within practical limits we are safe in using 
the heat of combustion (expressed in Calories) of any food- 
substance as a controlling measure of food values. The re- 
quisite number of Calories must, however, be obtained by 
the utilization of such substances as contain all the elements 
needed by the body, and in such ratio as has been found avail- 
able for the balance of nutrition. In carrying on its multi- 
farious activities the body loses about 20 grams of nitrogen 
per day, which must be replaced by the same element in the 
food taken. Thus while the requisite number of Calories may 
be furnished by fat or starch, these substances alone will not 
suffice for complete nutrition. The nutritive ratio, or the 
proportion of nitrogenous to non-nitrogenous food, must be 
maintained in the proportion of 1 to 3, or at least 1 to 5. 

The following table of one hundred common food-mate- 
rials is arranged in the order of calorific or energy-giving 
power, but in considering the food value of any one substance 
its nitrogen content must also be considered, and such com- 
binations made as will yield the requisite elements for a well- 
balanced ration. 

From even a cursory examination of the table it will be 
seen how widely some of the foodstuffs differ under differing 
conditions of soil moisture, fertilization in the case of plants, 



130 



AIR, WATER, AND FOOD. 



COMPOSITION OF SOME COMMON FOOD-MATERIALS AS PURCHASED* 

I. Fuel Value 3000-4000 Calories per Pound. 



Food-material. 


Refuse. 


Water. 


Nitroge- 
nous 
Substances. 


Fat. 


Carbo- 
hydrates. 


Butter 


Per cent. 


Per cent. 

II. o 


Per cent. 
1 


Per cent. 

85.0 
100.00 

83.0 
80.3 to 94.1 
70.7 to 94.5 

63.4 


Per cent. 












9-5 
0.3 to 12.2 
4.3 to 21.9 

2.5 


1.2 
0.2 to 5.0 
1.1 to 7.5 

16.6 










Suet 






Walnuts (shelled) 




16. 1 



II. Fuel Value 2000-3000 Calories per Pound. 



Bacon 

Cheese (American pale). 

Chocolate.... 

Doughnuts 

Mutton flank (fat) 

Peanut butter 

Sausage (farmer) 



Barley (pearled) 

Beans (dried) 

Cake average (except fruit). 

Candy 

Cheese (Neuchatel) 

Corn-meal 

Corn-starch 

Crackers (average) 

Fat meats 

Gelatin 

Ham (smoked, medium fat). 
Infants' and invalids 1 foods. 

Macaroni 

Oats .. . 

Peanuts 

Peas (dried) 

Pop-corn 

Rice 

Rye flour 

Sugar (granulated) 

Wheat (entire) flour 

Wheat flour (white bakers'). 

Wheat (shredded) 

Zwieback 




18.4 

31.6 
1.5 to 10.3 
[I.O to 25.8 

28.9 



9-5 

28.8 
12.5 to 13.4 
5.1 to 7.6 

10.7 

29-3 

27.9 





59-4 




35-9 


47 


1 to 50.2 


16 


4 to 25.7 




59-8 




46. 5 




40.4 



III. Fuel Value 1500-2000 Calories per Pound. 



11. 7 



4.5 to 28. 



9.8 to 12.9 
9.6 to 15.5 

19.9 
4.0 

42.7 to 57.2 

8.8 to 17.9 
10. o 

6.8 

38.3 

13.6 
27.3 to 42.5 
2.4 to 12.3 

7.0 to 12.3 
7 .8 
6.9 

6.9 to 15.0 

4-3 

9.1 to 14.0 
11. 9 to 13.6 



6.4 to 13. 1 
10. 1 to 13.3 

7.2 to 10.7 
5.0 to 7.7 

* Including fibre. 



7.0 to IO. 1 

19.9 to 26.6 

6-3 



15. 1 to 22.3 
6.7 to 11.6 



10.7 

13.0 

84.2 
10.2 to 21.9 
2.0 to 22.5 
7.9 to 16.6 

16.5 

i9-5 
20.4 to 28.0 

10 7 
5.9 to 11.3 
4.9 to 8.8 



12.2 to 14.6 
10.3 to 14.9 
9.6 to 11. 4 
8.6 to 11. 7 



.7 to 1.5 

.4 to 3.1 
9.0 



22.3 to 32.5 
1.0 to 5.3 



36.8 

O.I 

24.5 to 39.9 
0.3 to 10.9 
0.0 to 4.9 

7-3 

29.1 

0.8 to 1.3 

5-0 

0.1 to 0.7 
0.2 to 1.3 



0.3 

26.8 to 33.8 
45.8 to 63.2 



77.3 to 78.1* 
57.2 to 63.5* 

633 

96.0 

2 tO 2.9 

68.4 to 80.6* 
90.0* 

71.9* 



1.5 tO 2.1 

1.9 to 2.0 
1.3 to 1.6 
8.1 to 11. 3 



66.9 to 89.4 

67.2 to 78.4* 

66.5* 

18.5 

58.0 to 67.4* 

78.7 

75-4 t'> 81.9*- 
77.6 to 80.2* 

100 
69.5 to 77.0* 

70.3 to 75.5 
75.0 to 79.7* 

72.1 to 74.2 



IV. Fuel Value 1000-1500 Calories per Pound. 



Apples (dried) 

Bread (white) 

Corn-bread 

Dates , 

Figs 

Fresh pork (ribs and shoulder), 
Medium fat mutton and beef.. 

Mince-meat (commercial) 

Mince-meat (home-made) .... 

Pies 

Prunes (dried) 

Raisins 

Sandwiches 

Sardines (canned) 

Salt mackerel 



15.9 to 20.3 
14.4 to 27.8 



150 
10.0 



8.6 to 47.4 

35-3 
28.4 to 48.0 

13.8 
11. 6 to 25.0 
40.1 to 43.6 
38.0 to 44.9 

27.7 

54-4 

44.9 

19.0 

I3-I 

44.9 

53-6 

32.5 



1.2 tO 2 


5 


9.2 




6.5 to IO 


. 1 


1.9 




2.6 to 5 


7 


13.7 to 14.5 


II. 4 tO 12 


•9 


6.7 




4.8 




4.4 




1.8 




2-3 




10.9 




23-7 




16.3 






48.6t086.9E 

53-1 
40.3 to 54.3 

70.6 
68.3 to 83.1 



60.2 
32.1 
39-2 
62.2 
68.5 
33-3 



FOOD IN RELATION TO HUMAN LIFE. 



131 



COMPOSITION OF SOME COMMON FOOD MATERIALS. — Continued. 

V. Fuel Value 500-1000 Calories per Pound. 



Food-material. 



Beef (round) 

Beef (sirloin steak). 

Chicken (fowls) 

Cream 

Eggs , 

Herring (smoked). . 

Meats (lean) ... 

Olives . . 

Salmon (fresh) . . . 
Salmon (canned")... 
Tapioca pudding. . 

Tongue (beef) 

Turkey 

Veal (breast) 



Refuse. 



Per cent. 

8.5 

12.8 

18.0 to 42.7 



44.4 
0.5 to 11. 3 

"19.0 
23.8 to 35.. 
11. 7 to 16.9 



9-2 to 55.3 
17.1 to 32.4 
15.7 to 25.4 



Water. 



Per cent. 

62.5 

54.0 
38 3 to 53.7 

74.0 

65-5 

19.2 
59.9 to 69.2 

52-4 
45.0 to 51.2 
54.6 to 58.2 

52.0 to 71.6 

32.4 to 69.2 

41. 1 to 44.7 

48.5 to 55.7 



Nitroge- 
nous 
Substances. 



Per ce.it. 
19.2 
16.5 

11. 5 to 16.0 
2.5 

11.9 
20.5 

18. 1 to 21.4 

1.4 

12.6 to 15.0 
18.6 to 20.2 

2.8 to 4.2 
7.8 to 20.2 
15.8 to 16.8 

14.2 to 16.9 



Fat. 



Per cent. 

9.2 

16. 1 

6.9 to 21.5 

18.5 

9-3 

8.8 

7.8 to 14.2 
21.0 

6.6 to 9.5 
5.6 to 9.8 

2.3 to 4.8 
0.7 to 15.3 

5.9 to 25.5 

9.4 to 12.8 



Carbo- 
hydrates. 



Per cent. 



21.9 to 38.1 



VI. Fuel Value 400-500 Calories per Pound. 



Beans (canned red kidney). 

Calf 's-foot jelly 

Salt cod (boneless) 

Succotash (canned) 

Sweet potatoes 



72.7 
77 .6 
54.8 
.4 to 79.9 
55-2 



7.0 

4-3 

27.7 

2.9 to 4. 

r-4 



0.7 to 



18. 5 
17.4 



14.9 to 22.4 
21.9 



VII. Fuel Value 300-400 Calories per Pound. 



Bananas. .. . 
Butter beans 
Fish (fresh) . 

Grapes 

Hash 

Milk 

Potatoes 



Apples , 

Chicken (broilers). 

Cranberries , 

Onions 

Oysters (solid) — 

Parsnips , 

Pears 



3^.0 

50.0 

25.2 to 46.0 

25.0 



250 
.41055-1 



20.0 
10. o 



48.9 
29.4 

46.1 to 49. 
58.0 
80.3 
87.0 
62.6 



63.3 

44.6 to 52.4 
87.6 to 89.5 

78.9 

82.2 to 92.4 

66.4 

76.0 



0.8 

4-7 
11. 9 to 12.0 


0.4 

0.3 
1.8 to 5.9 

1.2 
1.9 
4.0 
O.I 

Pound. 

°-3 
1.1 to t.8 
0.4 to 0.9 

o-3 
0.5 to 1.8 

0.4 

0.4 


14-3 

14.6 


1.0 
6.0 
3-3 
1.8 

)RIES PER 

03 
9.0 to 15.7 
0.4 to 0.5 

1.4 
4.5 to 7.3 

x-3 

0.5 


14.4 
9.4 
5-0 

14.7 

10.8 


9.3 to 10.9. 

8.9 
1.5 to 6.2 

10.8 
12.7 



IX. Fuel Value 100-200 Calories per Pound. 



Beets 

Cabbage 

Carrots — , 

Green corn 

Lemons 

Oranges 

Soups (canned) 

Spinach.. 

Squash 

Tomatoes (canned). 



20.0 
15.0 
20.0 
61.0 
30.0 
27.0 



73.0 

77 7 

70.6 

29.4 

62.5 

63-4 
91.0 to 92.8 
91.6 to 92.8 

44.2 
92.5 to 97.9 



i-3 
1.4 
0.9 
1.2 

0.7 
0.6 

2.Q tO 5.O 

1.8 to 2.4 

o 7 
0.3 to 1.7 



0.2 

0.4 
0.5 



to o. 
to o, 



X. Fuel Value 10-100 Calories per Pound. 



Asparagus.... 

Bouillon (canned). 

Celery 

Cucumbers 

Watermelons 



20.0 
150 
59-4 



94.0 
96.5 to 96.7 
75-6 
81. x 
37-5 



1.8 
1.7 to 2.6 
0.9 
0.7 
0.2 



0.2 
0.0 to 0.2 

O.I 

0.2 

O.I 



7-7 

4.8 

7-4 

7-7 

5 9 

8.5 
0.6 to 5.7 
3.1 to 3.4 

4-5 
1.4 to 8.x 



3-3 

to 0.3 
2.6 
2.6 
2.7 



132 



AIR, WATER, AND FOOD. 



and of fatness or leanness in animals, of method of prepara- 
tion or of combination in cooked foods. 

Therefore examinations of materials are imperative if 
there is to be any basis of calculation. In an institution where, 
for instance, flour forms two-thirds of the daily ration, if it 
contains the lowest per cent, of nitrogen it may not furnish 
sufficient proteid for a well-balanced ration, or if the meat 
used is very lean there may not be fat enough for the best nu- 
trition. 

The great variation in the proportion of water leads to 
many surprises, and the amount of unedible material is to be 
considered. The uneducated provider buys oysters under the 
impression that he is furnishing food of high value, and does 
not distinguish between potatoes and rice. 

In the present state of our knowledge, the best use to 
which we can put such tables and analyses is as a check 
against gross errors of diet, which are found with alarming 
frequency especially among children and students, those who 
can least afford to make them. References will be found in 
the Bibliography to works for further study along these lines. 

Dietaries. — A dietary is simply a known amount of food of 
known composition per person per day, week, or month. 

What is called a standard dietary is such a combination of 
food-materials as shall furnish the amounts held to be neces- 
sary. The following are examples of such standard dietaries: 



Approximate Amounts 
required daily by- 


Nitrogenous, 
grams. 


Fats, 
grams. 


Carbohydrates, 
grams. 


Calories. 


Child of 6-9 


62 

78 

IOO 

100 

125 


45 

45 
75 
90 

125 


200 
28l 

380 
450 
500 


1593 
1890 
2665 
3092 
3725 




Adult at rest 


Adult at moderate work 
Adult at hard work. . . 



(In feeding experiments from 10 to 20 per cent, more must be allowed 
for waste and indigestibility.) 



FOOD IN RELATION TO HUMAN LIFE. 1 33 

From the table on p. 130 may be selected such food as will 
give the required quantities in variety enough to suit any taste. 
That which the table cannot give is the percent, of each which, 
under any given condition, will be utilized by the person fed. 
The strength of the digestive juices, exercise, fresh air, the 
cooking, the mixing of the foods, the habits of mind as to 
food, the customs of the family, all influence this utilization, 
so that other means must be resorted to in order to gain an 
idea of what is practicable. This is done by taking account 
of the food of persons free to choose ; of those in different 
countries, in different circumstances, and using a great 
variety of materials. Since Voit made his standard dietary in 
1870, many hundreds, at least, have been so gathered in the 
United States alone — more than two hundred since 1886. All 
the information thus gained goes to confirm the theoretical 
standard, and also to show how much depends upon suitable 
preparation and combination. These last two things help 
each other. 

As food is ordinarily prepared, about 10 per cent, must 
be deducted for indigestibility in a customary mixed diet, and 
about 10 per cent, more for the refuse or waste of food as 
purchased, so that of the total pounds of meat, vegetables, 
and groceries some 20 per cent, is of no final service in the 
body. It is immaterial whether this amount is subtracted 
from the final calculation or whether the higher figures be 
taken, that is, whether 125 grams of proteid as purchased or 
100 grams final utility is used. There will be an unknown 
limit in either case. According to late experiments 100 
grams of proteid is high. The waste of fats is less in propor- 
tion as the dietary is a restricted one. 

Knowledge of Food Values Necessary. — The most serious 
aspect of the food question is that the taking of it is volun- 
tary, not, like air, a necessity beyond control, and that the 



134 

most fantastic ideas are allowed to rule. The day-laborer is 
in little danger, since his food demand is made strong by out- 
of-door exercise; but the student who shuts himself up in 
hot, close rooms, and who does not look upon food as his 
capital, but only as a disagreeable task or an amusement, is in 
great danger, as is he who, having heard that one can live on 
a few cents a day, proceeds to try it without knowledge, and 
suffers a loss of efficiency for years or for all his life. 

It is not nearly so difficult to acquire a working knowl- 
edge of food values as of whist or golf, so that on entering a 
restaurant a suitable menu may be made up within one's al- 
lowance. It is only necessary to correct prevailing impres- 
sions and reinforce one's experience. 

Figs, dates, raisins, and prunes are apt to be regarded as 
luxuries instead of as rich food-substances of a most di- 
gestible kind when freed from skin and seed. Nuts are a 
much neglected form of wholesome food, admirably suited 
to a winter table from their richness in fat, and also furnish- 
ing muscular energy, as is seen in the agile squirrel, and is 
proved by many human examples. With nuts, however,, 
must be taken fruits or other bulky foods, to balance the con- 
centration. The somewhat compact and oily substance must 
be finely divided and freed from its astringent skin. 

In distinction from these rich foodstuffs, we find oranges, 
apples, etc.; the usual garden vegetables, asparagus, lettuce, 
etc., which, while they fill an important place in the dietary, 
add little directly to the energy of the body and need not be 
considered except as, by their flavor or aesthetic stimulus, 
they add to the efficiency of the rest. 

In looking over some housekeeping bills of a family not 
given to extravagance, but with a well-stocked market at 
hand and no especial check on the cook's orders, it was found 
that the ten staple articles cost 50 per cent, of the whole, the 



FOOD IN RELATION TO HUMAN LIFE. 1 35 

really nutritious foods of higher price 20 per cent., and the 
mere accessories 30 per cent. 

These accessories are truly cheaper than doctors' bills, and 
a high rate of efficiency in human mechanics is worth attain- 
ing even at a considerable expense. The chief difficulty lies 
in a subject outside the scope of these pages, namely, waste 
of the expensive or less nutritive material, or substitution of 
these for others more nutritive. For instance, a meal of 
lettuce dressed with oil, eaten with bread and cheese, fulfils 
all the requirements of nutrition, and may cost five cents. The 
same food value from sweetbreads, grape-fruit, etc., might 
cost a dollar. 



CHAPTER IX. 

THE PROBLEM OF SAFE FOOD. ADULTERATION AND 
SOPHISTICATION. 

Where food-materials are abundant, of known value, 
and without foreign admixture, there the general welfare of 
the people is satisfactory, barring sanitary errors in other 
directions. Where opportunity is given for the unscrupu- 
lous dealer to increase his gains at the expense of the health 
and lives of the people, children especially, it is eagerly 
seized upon, and milk diluted with water, colored with coal- 
tar products, and preserved with borax or formaldehyde is 
furnished so long as the community is ignorant enough to 
permit it. 

In frontier towns baking-powder containing alum is still 
sold, and in many places ginger containing 50 per cent, of 
turmeric, buckwheat, and redwood sawdust is on the market. 

The average buyer is content to go by familiar appear- 
ance, and is quite satisfied if he sees a dead bee in his honey 
and the usual form and color in his coffee-bean. Scientific 
skepticism has not yet touched the purchaser of the essentials 
of life, and manufacturers are not slow to perceive and to 
take advantage of his credulity. It is not necessary to resort 
to poisonous material or to directly deleterious substances; 
it is only necessary to mix a cheaper but equally wholesome 
material with a favorite article, or to substitute it altogether. 

To meet the craving for variety it is only necessary to make 

136 



THE PROBLEM OF SAFE FOOD. 1 37 

slight changes in the outward appearance of common sub- 
stances and then to advertise widely the discovery of some 
new process by which the food value is increased tenfold. 
In order that the community may be supplied with safe food, 
as well as with safe water, the education of the individual is 
important, even essential, since food is even more completely 
under individual control than is water. It is true that State 
and municipal regulations exist and should be enforced as 
to palpably noxious substances and those that are notoriously 
fraudulent. The relation of the citizen to these is the same 
as to the purity of the water-supply; it is his duty to uphold 
the hands of the authorities in the necessary expense of in- 
spection and prosecution. 

Adulteration and Sophistication. — To adulterate is defined 
as to debase, " to make impure by an admixture of baser 
materials, as in the case of coin, liquors," etc. 

As an explanation of sophistication, which is often used 
as synonymous with adulteration, this quotation is given: 
" These men have obscured and confounded the nature of 
things by their false principles and wretched sophistry.' , 
(South.) 

The sophists were educated and intelligent men, and per- 
suaded the people by specious reasoning. The modern 
" pure food " manufacturer is a sophist who, with great skill 
and by the aid of the well-paid expert, persuades the general 
public that he is their benefactor in that his chemists have 
penetrated nature's secrets, hidden from the ordinary man, 
and therefore that he is able to offer them long life and pros- 
perity at so many cents the pound. 

Although the words " adulteration " and " sophistica- 
tion " are in a degree synonymous, yet there is a distinction 
which seems borne out in legal practice. To adulterate the 
coin of the realm or the liquor of the bar with a baser metal 



I38 AIR, WATER, AND FOOD. 

or an imitation whisky is a heinous offence. So is the mix- 
ture of milk with the baser article, water, which thereby low- 
ers its food value. But the " wretched sophistry " which 
obscures the nature of things on a package of prepared food 
misleads more persons and inflicts more injury upon the com- 
munity than the other, yet goes unrebuked. The most 
barefaced assertions are printed in magazines, and " pure- 
food shows " only whet the appetite for something new. 

Predigested Foods. — This craving for something new to 
stimulate a jaded appetite already spoiled by endless variety 
and bad combinations has led to the manufacture of a cereal 
preparation for nearly every day in the year. No better com- 
mentary on the laziness or wilful ignorance of American pro- 
viders could be made than this. Little do the people know 
about wheat or cooking if they suppose that grain can be 
changed by manipulation in any kind of machine so as to give 
greater food value than was contained in the grain. While 
it is true that some of these preparations are far better than 
the half-cooked grains found on so many tables, the fact re- 
mains that it is the cook and not the substance which is poor. 
The false statements on food packages of all kinds are so 
absurd that they would defeat their own purpose were they 
viewed in the light of common sense. It is not always best to 
have food which is too easily digested. 

" The excessive fear of indigestible food which prevails 
among the wealthier classes may lead to universal debility of 
the intestinal muscular walls." * This fear and the lack of 
exercise is working mischief especially among students. 
Colleges do not educate along the fundamental lines of 
health. To be sure, gymnasiums are becoming common, 
and sometimes exercise does correct bad habits of eating, but 

* Bunge: " Physiological Chemistry" (trans.), 1890, 83. 



THE PROBLEM OF SAFE FOOD. 139 

a knowledge of food principles should go along with it in 
order that the greatest efficiency may be obtained. 

A predigested food is quickly absorbed into the circula- 
tion, and hence a small quantity causes a sensation of fulness 
and satisfaction which, however, soon passes away and a 
faintness results. This is especially true of the sugars and 
dextrins. Frequent meals should go with these easily ab- 
sorbed foods. This rapid digestion is the cause of much 
pernicious eating of sweets between meals, which satisfies 
the appetite for the time being and prevents substantial 
quantities of other foods being taken at the time they are 
offered. 

A lack of responsibility for the energy which we owe to 
the world, an inconsiderateness for the suffering we bring 
upon others, leads us to walk upon the thin ice of mere whim- 
sical eating. 

Extent of Adulteration. — The proportion of food adul- 
terated in the sense of harmful additions has always been 
comparatively small; probably in no community has it 
ever reached 10 per cent, of the food sold. In States 
which have legal penalties it is undoubtedly below 5 per 
•cent. Such statements as that 90 per cent, of the food 
offered in any market is adulterated can only mean, if 
true at all, that 90 per cent, of all the names of materials 
sold in shops cover more or less fraudulent mixtures. For 
instance, flour is rarely adulterated; pepper, ginger, and 
mustard are nearly always heavily adulterated. For one 
pound of these substances sold, 1000 pounds, or more, of 
flour go out from the store. Looked at in this lig-ht the sub- 
ject assumes quite another aspect. A canvass of the State 
of Massachusetts in 1879,* before the passage of the law of 

* Ellen H. Richards: "The Adulterations of some Staple Groceries." 
Ann. Rep. Mass. State Bd. Health, 1879 (Supp.), 55. 



140 AIR, WATER, AND FOOD. 

1882 and subsequent restrictions, showed that the staple arti- 
cles were very little adulterated; that then, as now, it was the 
condiments, of which only a small quantity is used at any one 
time, which showed the highest per cent. 

The influence of a stringent law fairly well enforced is 
seen in the decrease of the adulteration of cream of tartar in 
samples examined, which fell from 42 per cent, in 1879 to 
5 per cent, in 1898. 

Of suspicious samples of foods, exclusive of milk, exam- 
ined in the latter year by the State of Massachusetts, only 
13.4 per cent, were adulterated. Since only suspected arti- 
cles were taken by the inspectors, the actual per cent, must 
be far below this. Estimated on the total quantity sold, it ia 
doubtful if more than one per cent, of food which can come 
under the law is adulterated in Massachusetts to-day. The 
records of localities without the legal protection of inspec- 
tion is not quite so good as those of the five States which have 
stringent laws, and yet it is doubtful if harmful adulteration is 
very prevalent. 

Trade Names. — Much of this so-called adulteration de- 
ceives only the ignorant buyer. " Strictly pure " is a well- 
understood trade term and means " with a certain per cent, 
of addition"; "pure" has a greater addition, as "pure" 
spices. Of patent and proprietary preparations, and those 
covered by a trade name, the sale is on the increase, so that 
the statement is justified that the frauds in foodstuffs are 
mainly commercial, and not harmful in a direct way. Among 
the most serious are those packages claiming to consist of 
gluten and to furnish a substitute for hearty food and those 
so largely used by students. " Gluten flour " is not what the 
uninstructed might think, that which is very rich in gluten, 
but is only a whole wheat, possibly a very little richer in 
nitrogen than ordinary flour. " What's in a name " is well 



THE PROBLEM OF SAFE FOOD. I4I 

understood by sardine-canners, bread-makers, restaurant- 
keepers, and grocers. The dealer caters to the people and 
goes no farther than they readily follow him. 

Special Cases. — The use of canned goods brings certain 
dangers in the dissolved metals from the cans or from the 
solder, also from a careless habit of allowing food to stand 
in the opened tins. The liking for bright green pickles and 
peas leads to coloration by copper salts. The demand for 
cheap jellies has developed a new industry. The parings and 
cores of apples prepared for drying are cooked, strained, col- 
ored, and flavored to make to the eye a fair imitation of rasp- 
berry, currant, and grape jelly, sold for 7 to 10 cents a 
tumbler. 

Flavoring extracts offer a fertile field for chemical sub- 
stitutes. 

The excessive use of preservatives is caused by the crav- 
ing for food out of season and out of place: for summer fruit 
in winter, for oysters a thousand miles inland, and by the 
urban demand for fresh milk, which must be brought at 
least one hundred miles and can be delivered but rarely under 
thirty-six hours from the farm. The difficulty even then of 
furnishing enough leads again to the dilution by water, either 
indirectly through the breed and feed of the cow or by direct 
addition. Again, the extensive demand for cream tends to 
encourage the topping of the milk. 

With this increase in quantity and in time of keeping 
fresh food comes also the danger of transmission of disease, 
which constitutes one of the worst dangers in food. It hap- 
pens with considerable frequency that thirty or forty cases of 
scarlet-fever are traced to a single farm; that typhoid-fever 
also is disseminated in the milk. Cream and butter are also 
subject to suspicion. During the years 1890 to 1899 nine 



I42 AIR, WATER, AND FOOD. 

experts reported on 339 samples of butter and found tubercle 
bacilli in 21 per cent, of them. 

The dangers in butter are largely increased by the prac- 
tice of " doubling " the yield by a treatment of milk with 
rennet and salt, " black pepsin," or other nostrums, which 
works a large proportion of curd into the butter, but also 
renders the mass much more liable to decomposition. Since 
the food value of curd is only half that of fat, and since 
it also carries more water, the fraud is serious on both sides. 

In many ways the bread-supply of a city needs looking 
after from a sanitary and economical point of view quite as 
much as the milk-supply. It is not at all improbable that, 
first and last, as much disease is caused by bread from un- 
sanitary bakeries, by badly baked bread, and by unduly light 
bread which has not sufficient food value, as by any other 
cause. 

Summary. — The chief dangers in food are from wrong 
proportions of proteid, fat, and carbohydrates, from ferment- 
able and irritating decompositions, from bad methods of 
cooking and unsuitable combinations, from transmission of 
micro-organisms either by exposure to dust or by contact 
with filthy hands or vessels, to a favorable medium for the 
growth of pathogenic germs. 

From this hasty survey it will be seen how little danger 
to health is incurred if only reasonable care is taken and if 
the always doubtful articles are avoided. 

Take, for instance, that most commonly adulterated class, 
spices. Who will say that it may not be better to eat corn 
and buckwheat and ground peas than pure pepper? Rice 
is certainly a more wholesome food than ginger, and starch 
than soda. Glucose is even more easily absorbed than cane- 
sugar. These are cases of frauds on the pockets, but possible 
blessings in disguise for the stomachs. When any com- 



THE PROBLEM OF SAFE FOOD. 143 

munity is so ignorant as to permit of such gross, out-of-date 
adulterations as alum in baking-powder, and gypsum in 
cream of tartar, they deserve to suffer. It is knowledge on 
the part of each intelligent citizen which will mend matters, 
even if it is only that kind of empirical knowledge that one is 
forced to learn in relation to electricity and steam in order to 
live in a modern house. 

The natural food-materials are so complex in composi- 
tion that one may well be led astray by outward appearances, 
and substances of the same proximate composition present 
themselves under so many guises that when the markets of 
our cities offer the food of all the nations of the earth, how 
shall the buyer know what he is getting? To outward seem- 
ing, the potato and the banana have little in common, but 
their food value is almost identical, with the advantage on 
the side of the banana. 

The general public is alarmed over newspaper reports 
not wholly disinterested, or is " instructed " by paid agents. 
People become accustomed to certain terms which are held 
up as scarecrows, and learn to look to the daily press rather 
than to the agricultural college for knowledge as to new 
or dangerous foods. 

The remedy lies in their own hands. Every high-school 
laboratory should contain a case of samples and charts 
of values, and it should be considered just as impor- 
tant for good citizenship that the child should have the tools 
of health put in his hands as that he should learn about bank- 
ing and interest. His bank account is his health. His in- 
terest is his daily efficiency. 

So rapidly do new substances come upon the market that 
it is of little use to put into a general text-book definite 
statements of the quality of many foods. A baking-powder 
or a spice which is honestly made to-day may next week pass 



144 AIR > WATER, AND FOOD. 

into the hands of unscrupulous dealers who please the public 
and thereby salve their consciences. 

To furnish what the people think they want has been the 
rule from the days of an earlier generation of grocers, who 
divided a barrel of cooking-soda in halves and set one-half 
on one side of the store for " saleratus " and the other on the 
opposite side for soda, so that there should be no suspicion 
in the mind of the customer that the packages came from the 
same barrel, and yet each might satisfy his individual prefer- 
ence. 

We wish to dwell more strongly on the ethical and hy- 
gienic side of the question than on the financial. Evil-doers 
thrive only when reputable people countenance them. 
Adulterated food will be offered only so long as buyers 
eagerly take it. " Those that hide can find." If science is 
called upon to sophisticate food, science can find out how it 
is done. The chemist should be so grounded in morals as 
to refuse to sell his knowledge for a manufacture which is 
dangerous to health. We have tried to show that it is not 
very frequently the case that the manufactured article is of 
itself directly injurious, only in its misuse. 

It may be a question which is the cheaper, to build a sub- 
way or to kill a few persons now and then by the surface 
cars. So in food, it is necessary either to put an elaborate 
machinery of inspectors and chemists and courts in motion, 
at great expense, or to educate the people at large so that 
each will be his own inspector. The latter is more in har- 
mony with American practice, but the economic conditions in 
other directions are pressing the food-supply into the same 
channels as clothing, furniture, and transportation; that is,, 
away from individual control as to manufacture. This neces- 
sitates individual knowledge in purchasing if satisfactory re- 
sults are to follow. 



THE PROBLEM OF SAFE FOOD. 145 

This knowledge is now easily obtained through the city, 
State and government laboratories, and their publications 
are accessible to all who can read and write. There is, there- 
fore, no excuse for general ignorance and credulity as to 
trade preparations of foods, any more than for the degrading 
habit of purchasing patent medicines to remedy the ills 
caused by the misuse of food. Both together form the sad- 
dest commentary on human weakness and lack of rational 
thought 



CHAPTER X. 

ANALYTICAL METHODS. 

In the discussion of the methods employed for the ex- 
amination of food-materials, only a few typical substances 
have been considered, and the processes given are such as to 
bring into prominence the scientific aspect rather than the 
technical detail of the subject; at the same time it is hoped 
that a sufficient variety of methods is given to enable 
the student to gain considerable experience in the necessarily 
short time which can be allotted to the subject. 

Both on account of its importance as a food-material and 
on account of its availability for the various tests, milk has 
been chosen as a type of animal food; moreover, it may be 
made to serve as an excellent example of the changes to 
which food-materials are liable through the growth of the 
micro-organisms. The analysis of milk includes determina- 
tions of specific gravity, water, or total solids, ash, fat, nitro- 
gen, and sugar, together with the separation of casein and 
albumin, the determination of the products of putrefaction 
and fermentation, namely, ammonia and acidity, also the de- 
tection of preservatives and coloring matters. 

Wheat is taken as a type of vegetable foods. The ex- 
amination which may be made of this class includes the de- 
termination of moisture, ash, fat, nitrogen and proteids, 
starch, cellulose, and the products of peptonization and 

saccharification. 

146 



food: analytical methods: milk. 147 

The nature and composition of the various fats and oils 
is briefly illustrated by the examination of butter and the de- 
termination of the principal constants of the butter-fat. 

The results of fermentation are illustrated by the deter- 
mination of alcohol in beer, wine, meat extracts, patent medi- 
cines and " temperance drinks," flavoring essences and the 
like. The determination of the acidity, of the " extract," and 
of nitrogen is also sometimes desirable. 

Condiments, spices, tea, and coffee are generally exam- 
ined by means of microscopic tests, but adulterations of 
these, as of most common groceries, affect the health less 
than the pocket. Text-books on food adulteration furnish 
sufficient information on these points. (See Bibliography, 
P- 2I 3-) 



MILK. 

General Statements. — Milk is an emulsion of fat-globules 
with casein and other nitrogenous bodies, mineral salts 
(probably in combination), sugar and water. The average 
percentage composition of the more important varieties of 
milk, as found by recent observers, is summarized in the fol- 
lowing table: 

Water. Sugar. Proteids. Fat. Ash. 

Cow 86.90 4.80 3.60 4.00 O.70 

Human 88.75 6.00 1.50 3.45 0.30 

Goat 85.70 4.45 4.30 4.75 0.80 

Ass 89.50 6.25 2.00 1.75 0.50 

Mare 90.75 5'7° 2.00 1.20 0.35 

Sheep 80.80 4.90 6.55 6.85 0.90 

In connection with this table should be noticed the high 
proportion of sugar and low proportion of casein and ash in 
human milk as compared with cow's milk. The former is not 
readily curdled, the casein never separating in a compact clot 



I48 AIR, WATER, AND FOOD. 

which settles to the bottom, a difference which is attributed 
to the lower proportion of fat to casein.* 

The average composition of 120,540 samples of cow's 
milk, extending over a period of eleven years, and the aver- 
age composition of 14,135 samples of cow's milk for the 
year 1898, analyzed directly on arrival of the milk from the 
farm, is given by Vieth and Richmond f as follows: 

Average, 1898. Average of eleven years. 

Specific gravity 1.0320 

Total solids 12.73 12.90 

Solids not fat « 8.90 8.80 

Fat 3.83 4.10 

An examination of milk as regards its healthfulness usually 
consists in determining what changes, if any, have taken place 
in its constituents due to the growth of micro-organisms. 
Milk is a natural culture medium for the growth of micro- 
organisms and they increase in it with almost incredible 
rapidity. These changes which take place are called " fer- 
mentations." The two most common are the acid and the 
alkaline. 

Acid Fermentation. — Milk-sugar is converted wholly or in 
part into lactic acid under the influence of a class of organisms 
of which bacillus acidi lactici is the best known and is generally 
regarded as predominating. The extent to which this change 
has taken place is shown by the test for acidity. 

Alkaline Fermentation. — In the alkaline fermentation the 
albumin and casein are decomposed with the formation of 
ammonia and other intermediate nitrogenous products, some 
of them of a poisonous character, as is shown by the preval- 
ence of cholera infantum when such decomposed milk is used, 

* Lehmann and Hempel: Arch. Physiol., 56 (1894), 558. 
f Analyst, 17 {1892), 84; 24 (1899), 197. 



food: analytical methods: milk. 149 

and by cases of poisoning by ice-cream, etc. This fermenta- 
tion generally occurs simultaneously with the acid fermen- 
tation, but at first is much less active; at a subsequent stage, 
however, the alkaline fermentation becomes more pro- 
nounced, and in certain cases may completely dominate the 
other fermentations. 

Other Fermentations. — Butyric acid fermentation may be 
a result of the action of one or several groups of bacteria upon 
the glyceride of butyric acid. This action sets free the butyric 
acid in part and the fat becomes in time " rancid," but this 
change takes place, as a rule, more slowly and is not so com- 
mon as the others. 

The production of koumiss is an instance of an artificially 
incited change. Various other fermentations occasionally 
occur which cause a slimy appearance or a bitter taste. 
Various colors may be imparted to the milk by the presence 
of chromogenic or color-producing micro-organisms. The 
student is referred to the various journals and to text-books 
on dairy bacteriology for accounts of these less important 
changes. 

Sampling. — In all manipulations with milk the importance 
of thorough and frequent mixing, not shaking, cannot be too 
strongly emphasized; this is best accomplished by pouring it 
from one vessel to another. This will be found necessary 
even when the milk has been standing for only a few minutes, 
on account of the rapid rise of the cream. The apparatus 
used to contain or to measure milk should be thoroughly 
washed out as soon as possible. 

physical tests. 

Specific Gravity. — Take the specific gravity in the usual 
manner by means of a hydrometer or by the Westphal bal- 
ance, at 1 5 C. If the temperature of the milk varies from 



150 AIR, WATER, AND FOOD. 

1 5 , the reading may be corrected by means of Table IX, Ap- 
pendix A. Take a reading of the lactometer at the same time* 
In this instrument the minimum density for whole milk is 
fixed at 100, corresponding to a specific gravity of 1.029. 

Notes. — The specific gravity of milk is, in the main, a func- 
tion of two factors, namely, the percentage of solids not fat. 
and of the fat. The former raises it; the latter lowers it. The 
determination of the specific gravity alone is not to be relied 
upon as an absolute index of the purity of the milk. The 
specific gravity varies in general from 1.029 to 1.034, and in 
most cases of normal and well-mixed milk from several cows 
the specific gravity will lie between 1.030 and 1.032. 

Opacity. — The white color and opacity of milk are 
largely due to the presence of the suspended fat-globules and 
of the casein in colloidal form. The influence of the latter is 
shown by the fact that the color of milk is not greatly 
changed after it has passed through a centrifugal separator 
which removes practically all of the fat. The degree of 
opacity and the percentage of fat may be determined by 
means of Feser's lactoscope, the modus operandi of which is 
given with that instrument. Another instrument of like prin- 
ciple is Heeren's pioscope,* which consists of an ebonite disk 
with a raised rim; a drop or two of milk is placed upon it, the 
painted glass cover placed over it, and the color of the milk 
matched with one of those on the cover. 

Cream. — Fill the creamometer, an elongated test-tube 
with graduations near the top, to the zero mark with the 
milk, add three drops of a solution of methyl violet, mix and 
put away in a cold place. After twenty-four hours read off 
the percentage of cream. 

Notes. — The rapidity with which the cream rises indicates 

* Repit. f. Anal. Chem., 1881, 247. 



food: analytical methods: milk. 151 

whether sodium carbonate has been added, its action being 
to retard the rise of cream so that the milk is never blue. 
Should the cream separate very quickly and the milk be blue, 
the indication is that water has been added or that the milk 
is of poor quality. The method is only approximate and does 
not give the amount of fat. The methyl violet is added to 
render the reading sharper, as it does not dissolve appreciably 
in the cream. Cream contains most of the fat of milk with a 
small proportion of the other constituents. 1010 samples of 
cream gave an average of 48.3 per cent. fat. 

chemical tests. 

Reaction. — Normal milk gives the amphoteric reaction, 
that is, it turns delicate litmus both red and blue. This is due 
to the presence of neutral and acid phosphates of the alkalies.. 
The reaction of the milk soon becomes acid, however. 

Acidity. — Measure 5 c.c. of milk into a small beaker, 

N 
dilute with so c.c. of water, and titrate the acid with — 

sodium hydroxide, using phenolphthalein as an indicator. 
Express the acidity in degrees, considering each tenth of a 
cubic centimeter of sodium hydroxide one degree. 

Notes. — The acidity of milk is due to the fermentation of 
milk-sugar and the production of lactic acid. Under favor- 
able circumstances this change may take place with consid- 
erable rapidity. For example, six hours after milking the 
acidity may be fourteen to twenty-five degrees; forty-eight 
hours after milking it may reach one hundred degrees. When 
the acidity reaches .twenty-three degrees milk coagulates on 
boiling.* An example of the rate of change is given in the 
following table: f 

* Thorner: Analyst, 16 (i8gi), 200. 

f '« Thesis," Ethel B. Blackwell, M.I.T., 1891. 



152 AIR, WATER, AND FOOD. 

Dav Acidity, Sugar, 

t-'d-y- c.c. Degrees of Rotation. 

1 2.2 25-2 

2 5-5 23- 1 

3 • 11. o 21.6 

6 13.2 14.2 

7 15.0 9-4 

8 16.3 7 8 

9 17.2 1.2 

Alkalinity. — Directions. — Measure into a 750-c.c. round- 
bottomed flask 25 c.c. of the milk. Add 350 c.c. of ammonia- 
free water and 0.5 gram of sodium carbonate and distil over 
about 200 c.c. into a flask containing about 20 c.c. of dilute 
sulphuric acid (1:40). Neutralize the distillate with sodium 
carbonate and redistil it, receiving the distillate into 15 c.c. 

N 
(measured) of — hydrochloric acid. Titrate the excess of 

N 
acid with — sodium hydroxide, using methyl orange or 

cochineal as an indicator. 

Notes. — In the alkaline fermentation the proteids of milk 
are decomposed through the growth of micro-organisms. 
Ammonia, or some substance which yields ammonia on dis- 
tillation, is formed and tends to neutralize the lactic acid. 
On the other hand, abundant acid tends to check the growth 
of the alkaline ferments. It depends upon certain conditions 
of seeding and of temperature as to which gets the best start 
in the race. It is to the alkaline fermentation that most of 
the danger in using unsterilized milk is due. 

The second distillation which is made is for the purpose 
of converting into ammonia any amines which may have been 
formed during the first distillation. 

Total Solids. — The determination of total solids is best 
carried out in a platinum dish having a flat bottom about 2| 
inches in diameter. Small dishes of aluminum or blacking- 
box covers answer very well, but of course cannot be ignited 
to obtain the ash. 

Directions. — Weigh the platinum dish and add about 5.1 



food: analytical methods: milk. 153 

grams to the weights on the balance-pan. With the burette 
pipette deliver 5 c.c. of the well-mixed milk into the dish and 
weigh the whole as rapidly as possible to the nearest milli- 
gram. Evaporate the milk to dryness on the water-bath and 
then dry it in the oven at ioo° to a constant weight. Some 
analysts recommend drying at 105 ° for three hours instead of 
to constant weight. 

Notes. — It is important that the milk should be in the form 
oi a thin layer, so that the evaporation of the water shall take 
place as quickly as possible. Under these conditions the resi- 
due obtained is nearly white; but if the process be prolonged, 
it may have a brownish color from the caramelization of the 
sugar. 

Various analysts have proposed modifications of the pro- 
cedure as described above, such as drying on sand or asbes- 
tos, coagulation of the milk by absolute alcohol before evapo- 
ration, and so forth, but simple evaporation in an open dish 
is generally regarded as the most advantageous. 

Ash. — Directions. — Ignite the platinum dish containing 
the residue from the preceding determination at a low red 
heat until the ash is white or nearly so. In order to avoid 
too great a heat it is best to finish the ignition in a " radia- 
tor," as in the determination of the fixed residue in water- 
analysis. After weighing the ash, test it for carbonates by 
adding two drops of dilute hydrochloric acid. Effervescence 
in the ash is quite perceptible when carbonates are present in 
as small amount as 0.05 per cent. If desired, the hydrochloric 
acid solution of the ash can be used to test for boric acid as 
described on page 168. 

Notes. — If the temperature is raised too much during 
ignition, the results will be low on account of the partial vola- 
tilization of the chlorides of the milk; hence the process 
should be carried out at as low a temperature as will admit o£ 
the oxidation of the carbonaceous matter. 



154 AIR, WATER, AND FOOD. 

The percentage composition of the ash of milk is given 
by Fleischmann and Schrodt * as follows: 

Per cent. 

Potassium oxide, K a O 25.42 

Sodium " Na a O 10.94 

Calcium •' CaO 21.45 

Magnesium " MgO 2.54 

Ferric " Fe 3 3 0.11 

Sulphuric acid, SO3 4.11 

Phosphoric" P a 6 24.11 

Chlorine, CI 14.60 

103.28 
Less oxygen corresponding to chlorine f 3.28 

100.00 

The aoh of genuine cow's milk is free from carbonates and 
borates, and the ash soluble in water is about 30 per cent, of 
the total. 

Fat. — Since the fat is so important a constituent of milk, 
an endless variety of methods and modifications for its deter- 
mination have been devised. The processes which are in 
most general use may be divided into three classes: 

1. Estimation of the fat by simple extraction of the milk, 
best dried on some absorbent material. 

2. Volumetric estimation of the fat liberated by chemical 
treatment from the milk and collected by centrifugal force. 

3. Estimation of the fat by extraction from the milk itself 
after solution of the casein by acid. 

A typical method from each class will be described in de- 
tail. 

(1) Adams' Method. — Directions. — Roll a strip of fat- 
free blotting-paper, 22 inches long and 2\ inches wide, into 

* Baumeister: " Milch und Molkerei-Producte," S. 16. 

\ This correction is necessary because the metals are all calculated as 
oxides, when, as a matter of fact, a certain proportion are present as 
chlorides. 



food: analytical methods: milk. 155 

a rather loose coil and fasten it by a bit of copper wire. Hold 
the coil in one hand and carefully run on to the upper end of 
it 5 c.c. of milk from a burette pipette. Place the coil, dry 
end downward, in the water-oven and dry it for an hour. 
When dry remove the wire and place the coil in the Soxhlet 
extractor. If preferred, the strip of paper may be held hori- 
zontally in a frame and the milk run on to it. When dry the 
paper is roiled into a coil and extracted. Weigh the extrac- 
tion-flask, place in it 75 to 100 c.c. of 86° gasolene (petroleum 
ether) and connect the extractor with the condenser. After 
the coil has been extracted for about two hours remove the 
extractor, connect the flask with the suction if it is at hand, 
and distil off the gasolene under reduced pressure. The in- 
crease in weight of the flask gives the fat. Oxidation of the 
fat by too long heating should be avoided. 

A T otcs. — Absorbent paper exercises a selective action on 
the constituents of milk so that the fat is left on the surface 
of the paper, mixed with only about one-third of the non-fatty 
solids, and hence it is more easily extracted; further, owing 
to the greatly increased surface exposed, the extraction of the 
fat is practically complete. 

Ether may be used instead of gasolene, but care should 
be taken that the ether is perfectly dry, otherwise other sub- 
stances than fat, principally milk-sugar, will be extracted. On 
the other hand, substituted glycerides may not be dissolved 
out by ether. For these reasons the gasolene is to be pre- 
ferred as a solvent, although its action is considerably slower 
than that of the ether. 

Owing to the inflammable nature of the solvents em- 
ployed, it is best not to use a flame as the source of heat, but 
to heat the flask by means of a steam- or water-bath. In this 
laboratory small electric, heaters about 4 inches in diameter 
are used and have been found safe and convenient. The com- 
plete apparatus is shown in Fig. 7. 



1 5 6 



AIR, WATER, AND FOOD. 



Another form of apparatus, devised by W. R. Whitney, 
which has been used with satisfactory results is shown in 




Fig. 7. — Apparatus for Fat Extraction. 



Fi: 






test 



CONDENSER 
COIL 



8. It consists of an ordinary 
tube, the lower part of which 
is heated by a steam coil. A coil of 
small brass tubing, carrying a stream 
of cold water, hangs in the mouth of 
the test tube and serves as a conden- 
ser. The paper coil hanging from the 
condenser is extracted by the use of 
about 10 c.c. of gasolene or ether. 

(2) Babcock Method. — Directions. 
— Measure 17.6 c.c. of the milk from a 
pipette into the long-necked, gradu- 
ated whirling-bottle. Measure out 
17.5 c.c. of sulphuric acid (sp. gr. 
1.83), and add it gradually to the 

milk, mixing the two thoroughly after each addition. 

Take care that none of the liquid spurts into the neck 



Fig. 8. 



food: analytical methods: milk. 157 

of the bottle. After mixing the milk and acid, and 
while the bottles are still hot, place them in opposite 
pockets in the centrifugal machine, in even numbers, 
and whirl them for six minutes, the large wheel making 
eighty to ninety revolutions per minute. Then remove the 
bottles and add hot water until the fat rises to the 8 mark on 
the stem. Again place the bottles in the machine and whirl 
them at the same rate as before for one minute. Then 
measure the length of the column of fat by a pair of dividers, 
the points being placed at the extreme limits of the column, 
the fat being kept warm, if necessary, by standing the bottle 
in hot water. If now one point of the dividers is placed at 
the zero mark of the scale on the bottle used, the other will 
indicate the per cent, of fat in the milk. 

Notes. — When the acid and milk are mixed the. mixture 
becomes hot from the action of the acid on the water in the 
milk and turns dark-colored on account of the charring of 
the milk-sugar. The casein is first precipitated and then 
dissolved. The fat is thus separated in a pure state from 
the other constituents of the milk. 

The fat obtained should be of a clear, golden-yellow color, 
and distinctly separated from the acid solution beneath it. 
If the fat is light-colored or whitish, it generally indicates 
that the acid is too weak, and a dark-colored fat with a 
stratum of black particles below it indicates that the acid is 
too strong. The best results will be obtained by the use of 
acid of the strength noted above. 

A violet color is sometimes produced when the first por- 
tions of the acid and milk are mixed. This frequently indi- 
cates the presence of formaldehyde. (See p. 168.) 

(3) Werner-Schmid Method. — Directions. — Measure 10 
c.c. of milk into a long test-tube of 50 c.c. to 60 c.c. capacity 
and add 10 c.c. of hydrochloric acid (sp. gr. 1.20). Place 



■i 5 8 



AIR, WATER, AND FOOD. 



the tube in boiling water and heat, with frequent shakings 
until the liquid turns dark brown, which generally requires 
about ten minutes. Do not heat it so long that the liquid 
turns black. Cool the tube thoroughly under the tap, add 
30 c.c. of washed ether or of a mixture of equal parts ether 
and petroleum ether, cork tightly and mix well by inverting 
the tube. Allow the tube to stand for a few minutes for the 
complete separation of the ethereal layer, then remove the 
cork and transfer the ether to a tared flask by means of the 
apparatus shown in Fig. 9. This consists of a cork carrying 
an ordinary glass T tube. Through the 
straight limb of the T tube slides a bent 
glass tube, which is turned up at the lower 
end. The tube is adjusted by sliding it 
through the rubber collar (C) so that the 
lower end rests just above the junction of 
the two layers. On then blowing gently 
in the side arm (S), the upper layer is 
forced out into the flask. Repeat the ex- 
traction three times after the first, using 
10 c.c. of ether each time and blowing it 
off into the flask. Distil off the ether, dry 
the residual fat and weigh. 

Notes. — It is almost useless to try to ex- 
tract the fat from milk by shaking it directly with a solvent. 
An emulsion is formed with the other constituents of the 
milk, and it is impossible to get a good separation of the 
solvent even with the centrifugal machine. This is probably 
due to the action of the colloidal casein, because it is found 
that when a complete or partial solution of the casein is 
effected it is comparatively easy to extract and separate the 
fat by a solvent immiscible with water. 

The ether which is employed should be well washed to 




food: analytical methods: milk. 159 

remove alcohol, and the heating with hydrochloric acid 
should not be continued too long on account of the liability 
of forming caramel products which dissolve in the ether. 
For that reason the process is not so well suited for use with 
condensed or highly sugared milks. Since lactic acid is 
slightly soluble in ether, it is better when working with sour 
milk to make the extraction with petroleum ether or a mix- 
ture of petroleum ether and ordinary ether. 

Relation between Specific Gravity, Fat, and Solids 
in Milk. — As has been stated already, the specific gravity 
of milk is, in the main, a function of two factors, namely, 
the percentage of solids not fat and that of the fat. The former 
raises it, the latter lowers it. Taken by itself it affords very 
little indication of the composition, but if any other item be 
known, it should be possible to find, by calculation, the other 
quantities, provided the assumption is true. The solids not 
fat are made up of several fluctuating constituents, but " nor- 
mal milk " seems to contain them in such a constant ratio 
that a calculation serves at least to detect an abnormal sam- 
ple. For example, given the specific gravity and solids to 
calculate the fat: 

Specific gravity = Gr. The amount which each per cent, 
of solids not fat raises the specific gravity = s. The amount 
which each per cent, of fat lowers the specific gravity = f. 
Total solids = T. Solids not fat = S. Fat = F. Gr = vS*^ 
— Ff; or, substituting for S its value T — F; Gr = (T — F) 
s — Ff. The uncertainty of the calculation lies in the val- 
ues of s and f, which have not been quite satisfactorily deter- 
mined. 

At different times various formulae have been proposed 
for this calculation, varying, as a matter of course, with the 
method of fat extraction employed. The one most exten- 



160 AIR, WATER, AND FOOD. 

sively used is that of Hehner and Richmond,* which is based 
on extensive observation and perfected processes of fat ex- 
traction. This formula is generally stated as follows: 

^=0.8597— 0.2186(9, 

where F represents the fat, T the total solids, and G the 
specific gravity — i.ooo(X 1000). 

The simple formula — F = T answers within the 

5 4 

limits of experimental error for normal milk, but not for 
skimmed or watered milk. 

Example. — Data: Gr = 1.0323; G = Gr — I X 1000 = 
32.3; T= 12.90. 

6 32 3 

-F= 12.90 — — -. F— 4.02 calculated, 3.99 found. 

A similar relation has been worked out for the proteids 
and sugar, so that from three determinations the whole com- 
position may be calculated. Example as above: 

Ash = .70 = A. 

Formula: P= 2.87+ 2.5^ — 3.33^— .68-^, 

Gr. 

or P= 36.12 + 1.75 — 13.32 — 21.28 = 3.27. 

Sugar =T-(A+ P+ F) 

= 12.90 - (.70 + 3.27 + 4.02) = 4.91. 

Where a number of calculations are to be made, Rich- 
mond's milk-scale will be found convenient. This is an in- 
strument based on the principle of the slide-rule, having three 
scales, two of which, for the fat and the total solids, are 
marked on the body of the rule, while that for the specific 
gravity is marked on the sliding part. Extended tables are 
also used for the same purpose. 



* Analyst, 13 {1888), 26; 17 {i8g2), 170. 



food: analytical methods: milk. 161 

Milk-sugar. — The methods for the determination of the 
sugar in milk may be divided into two general classes: (i) 
those depending on the reducing power of the sugar upon an 
alkaline copper solution; (2) those which are based upon ob- 
servations of the degree of rotation of the plane of polarized 
light. 

(1) Determination by Fehling's Solution. 

(a) Volumetric ally. 

Directions. — The milk must first be clarified to remove 
substances other than sugar which would exert a reducing 
action on the Fehling's solution. To do this, measure 25 c.c. 
of milk from a pipette into a 250-c.c. bottle. Add 0.5 c.c. 
(measured) of 25 per cent, acetic acid, shake vigorously, and 
allow it to stand for five minutes. Add 75 c.c. boiling dis- 
tilled water, shake, and let it stand two or three minutes. Add 
15 c.c. of milk of alumina (see determination of chlorine in 
water), shake, and allow the bottle to remain on its side for 
ten minutes. Decant carefully into a medium-sized beaker, 
and add hot water again to the residue in the bottle. Decant 
the liquid from the beaker on to a ribbed Swedish filter. Wash 
thus by successive decantations from the bottle to the beaker, 
and thence to the filter several times before bringing the 
precipitate on the filter. Make the filtrate up to 500 c.c. and 
mix thoroughly. The solution should be perfectly clear and 
almost without color. 

Titration. — Measure 5 c.c. of the copper solution from a 
burette into a 150-c.c. Erlenmeyer flask, add 5 c.c. of the 
alkaline tartrate solution and 40 c.c. of water. Heat to boil- 
ing and from a burette run in the sugar solution, as prepared 
above, as long as a blue color is seen in the liquid, which 
must be kept constantly boiling. When the end-point is ap- 
parently reached, test the solution for copper by filtering a 



162 AIR, WATER, AND FOOD. 

few drops through a very small filter on to a porcelain 
plate containing a dilute solution of potassium ferrocyanide 
strongly acidulated with acetic acid, when, if copper be pres- 
ent, the characteristic rose coloration will appear. This will 
give approximately the number of cubic centimeters required 
to decolorize the copper solution. 

To find the exact number, add the quantity of sugar solu- 
tion used above to a fresh portion of 5 c.c. of each solution 
and 40 c.c. of water, boil exactly two minutes, and test the 
solution for copper as before. If copper be still present, re- 
peat the operation, using 0.2 c.c, more or less, of the sugar 
solution each time until the end-point is reached. If 10 c.c. 
of Fehling's solution of the strength given are reduced by 

, , ... , 500 X .067 

0.067 gram of milk-sugar, then r— : -j = grams 

' ° c.c. solution used ° 

of milk-sugar in 25 c.c. of the milk. The results are reported 

in per cent. From 2y to 34 c.c. of the milk-sugar solution are 

usually required to reduce 10 c.c. of Fehling's solution. 

Notes. — The general principle upon which all these 
methods depend is based on the fact that certain sugars, 
among which is lactose, have the power of reducing an alka- 
line solution of copper to a lower state of oxidation in which 
copper is separated as cuprous oxide. The copper salt which 
is found to give the most delicate and reliable reaction is the 
tartrate. The two solutions which make up the Fehling's 
solution are best preserved separately, and mixed only when 
wanted for use, as otherwise the reducing power of the solu- 
tion is liable to change. 

The amount of reduction of the copper salt to the cuprous 
oxide is affected by the rate at which the sugar solution is 
added, the time and degree of heating, and the strength of 
the sugar solution; hence the necessity for adopting a 
definite procedure. 



food: analytical methods: milk. 163 

(b) Gravimetrically by weighing as Cupric Oxide* 

Directions. — To 15 c.c. of the copper sulphate solution add 
15 c.c. of the alkaline tartrate solution in a 150-c.c. Erlen- 
meyer flask. Add 50 c.c. of freshly boiled distilled water and 
place the flask in a boiling-water bath for five minutes. Then 
from a calibrated flask quickly add 25 c.c. of the sugar solu- 
tion to the hot Fehling liquor, leave the 25-c.c. flask inverted 
in the mouth of the larger one, and keep the whole in the 
boiling-water bath for fifteen minutes. At the end of this 
time remove the flask and filter off the cuprous oxide as 
rapidly as possible through a thick layer of asbestos in a 
weighed porcelain Gooch crucible. Wash with boiling dis- 
tilled water until the wash-water no longer reacts alkaline. 
Place the crucible in a platinum or nickel crucible and heat it, 
gently at first, then to a red heat for about fifteen minutes. 
Cool and weigh quickly, as the cupric oxide is somewhat 
hygroscopic. Convert the weight of cupric oxide into lactose 
by multiplying by the factor 0.6254, which will be sufficiently 
close for all ordinary work. If more accurate results are de- 
sired, consult Defren's table in the article previously men- 
tioned. 

Notes. — The asbestos which is used should be previously 
boiled in nitric acid and then in dilute sodium hydroxide and 
thoroughly washed. 

The amount of cuprous oxide produced by the action of 
one gram of reducing carbohydrate on Fehling's solution, in 
the manner described, is not a constant for all dilutions. For 
this reason the amount of lactose cannot be calculated ex- 
actly from the weight of cupric oxide, but reference must be 
made to the specially constructed table. Moreover, each 
table, whether Allihn's, Wein's, or Defren's, can be used only 

* Defren: Tech. Quart., 10 (/<?97), 167. 



1 64 AIR, WATER, AND FOOD. 

when the reduction is carried out under conditions similar to 
those employed in the determinations on which the table was 
based. 

(2) Determination by the Saccharimeter. — For the 
optical determination of milk-sugar the method of double di- 
lution, as described by Wiley and Ewell,* will be found satis- 
factory. 

Directions. — Into each of two flasks, marked at 100 and 
200 c.c, respectively, put 65.52 grams of milk, add 10 c.c. of 
acid mercuric nitrate, fill to the mark, and mix by shaking. 
Filter through dry filters and polarize in a 400-millimeter 
tube, using the Schmidt and Haensch saccharimeter. Cal- 
culate the results as in the following example: 

Weight of milk used = 65.52 grams; 

Reading from 100-c.c. flask = 2o°.84; 
" " 200-c.c. flask = io°. 15. 

Then 10. 15 X 2 = 20.30; 

20.84 — 20.30 = 0.54; 
0.54 X 2 = 1.08 ; 

20.84 — 1.08 = 19.76; 
19.76 -r- 4 = 4.94, which is the per cent, 

of milk-sugar. 

Notes. — The object in using the method of double dilu- 
tion is to avoid the necessity of making corrections for the 
volume of the precipitate of casein and fat. The method is 
based on the fact that, within certain limits, the polarizations 
of two solutions of the same substance are inversely propor- 
tional to their volumes. 

The flasks should be filled at nearly the same temperature 
as that at which the polarizations are made, and the tem- 

* Analyst, 21 {iSg6) % 182. 



food: analytical methods: milk. 165 

perature of the room should be kept as nearly as possible at 
20 to avoid errors arising from marked changes in tempera- 
ture. 

PROTEIDS OF MILK. 

Determination of Total Proteids. — Weigh 5 grams of 
milk into a 750-c.c. round-bottomed flask and determine the 
nitrogen by the Kjeldahl process as directed on page 183. 
Multiply the per cent, of nitrogen by the factor 6.25 to obtain 
the per cent, of proteids. 

Separation of Casein and Albumin.* — Directions, — 
To 5 grams of milk add 50 c.c. of a solution of magnesium 
sulphate (saturated at 40°-50°) and heat the mixture to 
about 45 until the precipitate settles out, leaving the super- 
natant liquid clear. Filter and wash the precipitate several 
times with the solution of magnesium sulphate prepared as 
above, keeping the temperature at about 45 . Determine the 
nitrogen in this precipitate and multiply by 6.38 for the casein. 
The difference between the total and casein nitrogen will be 
the amount corresponding to the albumin, together with the 
very small amount of globulin. 

Notes. — The principal proteid body present in milk is 
casein. Others present in much smaller quantity are albumin, 
peptone, and fibrin or globulin. Different observers at vari- 
ous times have claimed the presence of other nitrogenous 
bodies, but these have not been entirely substantiated. 

It is now generally held that the colloidal state in which 
the casein is held in milk is due to the combination with it of 
certain mineral compounds, chiefly those of calcium. The 
action of precipitants is on these mineral matters, breaking 
up the combination and releasing the insoluble casein. 

Sebelien: Ztschr. physiol. Chem., 13 (1889), 160. 



1 66 AIR, WATER, AND FOOD. 

Most authorities at present favor the factor 6.38 for cal- 
culating the casein, although the old factor 6.25 is still largely 
used. 

Adulterants. — The most common forms of adulteration 
of milk are the addition of water and the removal of cream. 
The former is detected by the decrease in the specific gravity, 
total solids and ash, and the latter by the increased specific 
gravity and greatly decreased amount of fat. Various sub- 
stances may also be added, such as salt, cane-sugar, or starch. 

Direct Determination of Added Water. — This is best done 
by determining the specific gravity of the milk-serum after 
coagulation and removal of the casein.* The casein is co- 
agulated by dilute acetic acid, filtered off on a dry filter, and 
the specific gravity of the filtrate taken at 15 C. by the West- 
phal balance. The specific gravity of the serum from normal 
milk is never below 1.027 and only rarely below 1.029. The 
addition of each ten per cent, of water lowers the specific 
gravity by 0.00 10 to 0.0035. 

Salt. — Detected by the high percentage of ash and deter- 
mined by titration with silver nitrate and potassium chromate 
either in the ash or in the milk itself after clarification with 
milk of alumina. 

Cane-sugar. — To detect the presence of cane-sugar boil 
about 10 c.c. of the milk with 0.1 gram of resorcin and 1 c.c. 
of hydrochloric acid for five minutes. The liquid will be col- 
ored rose-red if cane-sugar be present. The quantitative de- 
termination may be made by means of the polariscope. 

Starch. — Heat 10 c.c. of the milk to boiling in a test-tube, 
and when cold add a few drops of a solution of iodine in po- 
tassium iodide. The presence of even 0.2 per cent, of starch 
will be shown by the characteristic blue coloration. 

* Woodman: J. Am. Chem. Soc, 21 (i8gg), 503. 



food: analytical methods: milk. 167 

Coloring-matters.* — The principal coloring-matters 
added to milk are annatto, caramel, and aniline dyes. In 
general, coloring-matters are added only to watered milk, but 
occasionally samples which were of standard quality have 
been found to be colored. 

Directiotis. — Put about 100 c.c. of the milk into a small 
beaker, add 2 c.c. of 25 per cent, acetic acid and allow the 
beaker to stand quietly for about ten or fifteen minutes in a 
water-bath kept at 70° C, the casein being thus separated as 
a compact cake. Decant off the whey, squeezing the curd as 
free from it as possible by means of a spatula. Transfer the 
curd to a flask and let it remain covered with ether for an hour 
or more. 

Evaporate the ether extract which contains the annatto 
if present, take up the residue with water made faintly alka- 
line with sodium hydroxide and filter through a wet filter. If 
annatto is present, it will permeate the filter and give it an 
orange color when the fat is washed off and the filter dried. 
Treat the dried filter with stannous chloride. If annatto is 
present, a pink color will be produced. 

After pouring off the ether examine the milk-curd for 
caramel or aniline orange. If the curd is left white, neither 
of these colors is present. If caramel has been used, the curd 
will be of a pinkish-brown color; if the color is due to the 
aniline dye, the curd will have a yellow or orange tint. To 
distinguish between the two colors shake a small portion of 
the curd in a test-tube with strong hydrochloric acid. The 
caramel-colored curd will act similarly to an uncolored curd, 
that is, it will gradually produce a deep blue color in the so- 
lution. On the other hand, the aniline color will immediately 
produce with the hydrochloric acid a pink color. 

* Ann. Rep. State Bd. Health, Mass., 1898, 697. 



1 68 AIR, WATER, AND FOOD. 

Preservatives.— The preservatives usually added to milk 
are salicylic acid, borax or boric acid, formaldehyde, and 
occasionally benzoic acid and potassium chromate. Car- 
bonate of soda is also added in some cases to disguise the 
acidity of sour milk. 

Salicylic Acid. — To 50 c.c. of the milk add 10 c.c. of the 
acid mercuric nitrate used in the optical determination of 
milk-sugar, shake and filter. Shake the filtrate violently in 
a separatory funnel with 30 c.c. of a mixture of equal parts 
of ether and petroleum ether. Evaporate the ethereal solu- 
tion to dryness and add a drop of neutral ferric chloride 
solution to the residue. If salicylic acid is present, the char- 
acteristic violet color will be produced. 

Boric Acid. — Add 5 drops calcium hydroxide solution to 
10 (or 100) c.c. of milk and evaporate to dryness on a water- 
bath. Char the residue, add 2 c.c. water and a few drops of 
dilute hydrochloric acid, and filter into a porcelain dish. 
Test the filtrate in the usual way with turmeric-paper or by 
the alcohol-flame test. For the latter methyl alcohol is best. 
The tests for boric acid can also be applied to the hydro- 
chloric acid solution of the ash. 

Formaldehyde.— -This is generally used as a 40 per cent, 
aqueous solution, sold under the name of formalin. Several 
simple tests commonly used for the presence of formaldehyde 
will be described. 

(1) When the sulphuric acid is added to the milk in mak- 
ing the Babcock test for fat, a bluish-violet ring will be 
noticed at the junction of the two liquids when formaldehyde 
is present. One part of formaldehyde in 200,000 parts of 
milk can be detected by this test, but it fails when the for- 
maldehyde amounts to 0.5 per cent. The test is more 
delicate if the sulphuric acid contains a trace of ferric chlo- 
ride. 



food: analytical methods: butter. 169 

(2) To 10 c.c. of milk add 1 c.c. of fuchsin sulphurous 
acid and allow it to stand five minutes; it takes on a pink 
color whether formaldehyde be present or not. Then add 2 
c.c. of dilute hydrochloric acid and shake. Pure milk be- 
comes yellowish white, while milk containing formaldehyde 
gives a violet color. This test will detect 1 part of formalde- 
hyde in 20,000 parts of milk, and if applied to the distillate 
from the milk will show 1 part in 500,000. 

(3) To 10 c.c. of milk in a small porcelain dish add an 
equal volume of hydrochloric acid (1.12 sp. gr.). Add one 
drop of ferric chloride solution and heat the dish with a small 
flame, stirring vigorously, until the contents are nearly boil- 
ing. Remove the flame and continue the stirring for two 
or three minutes. The presence of formaldehyde will be 
shown by a violet color which appears in the particles of the 
precipitated casein, the depth of color depending on the 
amount of formaldehyde present. This test readily shows 
the presence of 1 part of formaldehyde in 500,000 parts of 
milk. 

Benzoic Acid. — Fres. Zeit., 21, 531; Jour. Anal. Chem., 2, 
446. 

Sodium Carbonate. — Detected in the milk-ash, as on 
page 153. If effervescence occurs, test the original milk with 
rosolic acid as follows: Mix 10 c.c. of milk with an equal 
volume of alcohol, and add a few drops of a one per cent, 
solution of rosolic acid. The presence of sodium carbonate 
is indicated by a more or less distinct pink coloration. A 
comparative test should be made at the same time with milk 
known to be pure. 

BUTTER. 

General Statements. — Butter consists of the fat of milk, to- 
gether with a small percentage of water, salt, and curd. 



170 AIR, WATER, AND FOOD. 

The curd is made up principally of the casein of the milk. 
These various ingredients are present in about the following 
proportions: 

Fat 78.00-90.0 per cent- ; average, 82 per cent. 

Water 5.00-20.0 " " " 12 " " 

Salt 0.40-15.0 " '■ " 5 " " 

Curd 0.11- 5.3 " " " 1 *' 

The fat consists of a mixture of the glycerides of the fatty 
acids. The characteristic feature of butter-fat is the extraor- 
dinarily high proportion of the glycerides of the soluble and 
volatile fatty acids when contrasted with other fats. 

Recent investigations * show the following to be the 
probable composition of normal butter-fat: 

Acid. Per cent. Acid. Per cent. Triglycerides. 

Dioxystearic 1.00 1.04 

Oleic 32.50 33-95 

Stearic 1.83 1.91 

Palmitic 38.61 40.51 

Myristic 9.89 10.44 

Laurie 2.57 2. 73 

Capric 0.32 0.34 

Caprylic 0.49 0.53 

Caproic 2.09 2.32 

Butyric 5.45 6.23 

Total 94-75 100.00 

According to this, the proportion of volatile acids in but- 
ter (butyric, caproic, caprylic, and capric acids) amounts to 
8.35 per cent. The amount of volatile acid in lard, for ex- 
ample, is about 0.1 per cent. 

The usual examination of butter consists in the examina- 
tion of the butter-fat, in order to detect the presence of foreign 
fats. The determination of the amount of curd may be of 
value also in some cases, more especially from a sanitary 

* Browne: J. Am. Chem. Soc, 21 (i8gg), 807. 



food: analytical methods: butter. 171 

standpoint. The chief danger to health probably lies in the 
possible decomposition of the nitrogenous portion, for it is 
quite generally recognized that the substitution of oleo- 
margarine is not injurious to health. It is a not infrequent 
practice, however, as remarked in the previous chapter, to 
incorporate a large amount (sometimes as high as 33 per 
cent.) of curd and other nitrogenous matters in fresh butter. 
If this is kept for any length of time, a decomposition is 
liable to occur which may have serious effects. Other de- 
terminations that are usually made are the water and salt. 

The " aroma " of butter seems to be connected with the 
decomposition produced by the action of bacteria on the 
casein and the small amount of milk-sugar that is present, 
and not with any change in the fats; there is no evidence, 
however, that any unwholesome effect is produced by the 
aroma-giving organisms. 

The rancidity of butter-fat is generally considered to be 
due to decomposition and oxidation of the fatty acids, espe- 
cially the unsaturated ones, the amount of change depending 
on conditions of light, heat, and exposure to air. 

Examination of the Fat. — The fat is first separated 
from the other constituents of the butter so that it may be 
weighed out for the various tests. 

Directions. — Melt a piece of butter, a'bout two cubic 
inches, in a small beaker placed on top of the water-bath so 
that the temperature shall not rise above 50°-6o°. After 
about fifteen minutes the water, salt, and curd will have set- 
tled to the bottom. (A better separation may be secured 
by pouring the melted butter into a test-tube and whirling 
it for 3-4 minutes in a centrifugal machine.) Place a bit of 
absorbent cotton in a funnel, previously warmed, and decant 
off the clear fat through the cotton into a second beaker, 
taking care that none of the water or curd is brought upon 



172 AIR, WATER, AND FOOD. 

the filter. When the filtered fat has cooled to about 40 
place a small pipette in the beaker and weigh the whole. 

By means of the pipette the desired amount of fat is taken 
out, the pipette replaced in the beaker, and the whole again 
weighed. The difference in weight gives the exact amount 
of fat taken. It is a saving of time, however, if several por- 
tions are to be weighed out, to make the weights one after 
another, so that one weight will suffice for a determination. 
Weigh out thus: Two portions of 5 grams each into 250-c.c. 
round-bottomed flasks for the Reichert-Meissl method, one 
portion of 2.5 to 3 grams into a 500-c.c. beaker for Hehner's 
process, two portions of about 1 gram each into 300-c.c. 
glass-stoppered bottles fo/ Hubl's process. 

(1) Reichert-Meissl Number for Volatile Fatty Acids. 
— Directions. — To the fat in the 250-c.c. flasks add 2 c.c. of 
strong caustic potash (1:1) and 10 c.c. of 95 per cent, 
alcohol. Connect the flask with a return-flow condenser 
and heat on a water-bath so that the alcohol boils vigorously 
for 25 minutes. At the end of this time disconnect the flask 
and evaporate off the alcohol on a boiling-water bath. After 
the complete removal of the alcohol add 140 c.c. of re- 
cently boiled distilled water which has been cooled to about 
50 . The water should be added slowly, a few cubic centi- 
meters at a time. Warm the flask on the water-bath until 
a clear solution of the soap is obtained. Cool the solution to 
about 6o° and add 8 c.c. of sulphuric acid (1:4) to set free 
the fatty acids. Drop two bits of pumice, about the size of 
a pea, into the flask, close it by a well-fitting cork, which is 
tied in with twine, and immerse it in boiling water until the 
fatty acids have melted to an oily layer floating on the top 
of the liquid. Cool the flask to about 6o°, remove the cork, 
and immediately attach the flask to the condenser. 

Distil no c.c. into a graduated flask in as nearly thirty 



food: analytical methods: butter. 173 

minutes as possible. Thoroughly mix the distillate, pour the 

whole of it through a dry filter, and titrate 100 c.c. of the 

N 
mixed filtrate with — sodium hydroxide, using phenol- 

phthalein as an indicator. Increase the number of cubic centi- 
meters of alkali used by one-tenth, and correct the reading 
also for any weight of fat greater or less than 5 grams. 

For example, if 5.3 grams of butter-fat are used, and 100 

N 
c.c. of the distillate require 27.4 c.c. of — NaOH, no c.c. 

would require 27.4 + 2.74 = 30.14 c.c. Then 5.3 : 30.14 = 
5 : x. x = 28.4. x is the Reichert-Meissl number. 

Notes. — The Reichert-Meissl number for genuine butter 
varies from 24 to 34; the average usually taken is 28.8. 
Oleomargarine gives a number of about 1.5 to 2. 

When the fat is treated with potash it is decomposed, the 
glycerine being set free, and the potassium salts of the fatty 
acids, that is to say, the potassium soaps are formed. Hence 
the process is called saponification. For butyric acid the re- 
action is 

C 3 H 5 (C 3 H 7 COO) 3 + 3KOH = 3 C 3 H 7 COOK + C 3 H 5 (OH) 3 . 

The alcohol is used to dissolve the fat. But at the 
moment the butyric acid is set free it tends to combine with 
the alcohol to form a volatile ether: 

C 8 H 7 COOH + C 2 H 5 OH = C 8 H.COOC 2 H 5 + H 2 0. 

The object of the return-flow condenser is to prevent the 
escape of this volatile ether and to allow of its complete 
saponification. 

If the water used to dissolve the soap is added too rap- 
idly, the soap may be decomposed with the liberation of the 
fatty acids: C 3 H 7 COOK + H 2 = C 3 H 7 COOH + KOH. 



174 AIR, WATER, AND FOOD. 

The fatty acids are set free at the proper time by means, 
of sulphuric acid, and the volatile acids distilled off and. 
titrated. The pumice is added to prevent explosive boiling. 

The whole of the volatile acids do not pass over into the 
distillate, but only a part, the amount depending upon the 
rate of distillation and the volume of the distillate. Hence, in 
order to get uniform results, it is necessary to follow the pre- 
scribed procedure with great care. 

(ia) Method of Leffman and Beam. — In order to 
shorten the time required for the saponification and subse- 
quent removal of the alcohol, Leffman and Beam * have 
proposed the use of a solution of sodium hydroxide in glycer- 
ine as the saponifying agent. 

Directions. — To the fat, weighed out into a 250-c.c. flask* 
as in the Reichert-Meissl method, add 20 c.c. of the glycerine- 
soda solution and heat the flask over a lamp. Boil the mix- 
ture gently until all the water has been driven off and the 
liquid becomes perfectly clear, which will usually be the case 
in about five minutes. Care should be taken to avoid loss, 
from spattering. Allow the flask to cool somewhat, and 
dissolve the soap in 135 c.c. of boiled distilled water. Add 
the first portions of water drop by drop, shaking the flask 
each time to avoid foaming. When the soap is dissolved, 
add 5 c.c. of sulphuric acid (1:4), two pieces of pumice, and 
carry out the distillation without previous melting of the 
fatty acids. The distillation and titration are completed as 
in the Reichert-Meissl process. 

(2) Hehner's Method for Direct Determination of 
the Fixed Fatty Acids. — Directions. — To the portion of 
2.5 grams weighed out into the 500-c.c. beaker add 1 e.c. of 
caustic potash and 20 c.c. of 95 per cent, alcohol. Cover 

* •■ Analysis of Milk and Milk Products" (Philadelphia, 1896), p. 78. 



food: analytical methods: butter. 175 

the beaker with a watch-glass and heat it on the water-bath 
until the liquid is clear and homogeneous. As it is not 
essential to prevent the escape of the volatile acids, the use 
of a return-flow condenser is not necessary. Evaporate off 
the alcohol on the water-bath and dissolve the soap in about 
400 c.c. of warm distilled water. When the soap is com- 
pletely dissolved add 10 c.c. of hydrochloric acid (sp. gr. 
1. 12), and heat the beaker in the water-bath almost to boil- 
ing until the clear oil floats. Meanwhile dry and weigh a 
thick filter in a small covered beaker. Allow the solution to 
cool until the fat forms a solid cake on top; filter the clear 
liquid and finally bring the solid fats upon the weighed filter. 
Wash the beaker and fat thoroughly with cold water, then 
wash out the fat adhering to the beaker with boiling water, 
which is poured through the filter, taking care that the filter 
is never more than two-thirds full. Cool the funnel by 
plunging it into cold water, remove the filter, place it in the 
weighing-beaker and dry it at ioo° to constant weight. The 
fat should be heated about an hour at first, then for periods 
of about fifteen minutes, until the weight is constant within 
2 mgs. 

Notes. — 87.5 per cent, is usually taken as the proportion 
of fixed fatty acids in butter-fat; 88 and 89 per cent, have 
been frequently found. All other fats yield from 95 to 96 
per cent, of insoluble fatty acids. 

(3) Method of Baron Hiibl. — This method is based on 
the fact that certain of the fatty acids, notably the " unsatu- 
rated acids," as oleic acid, C 17 H 33 COOH, take up the halo- 
gens with the formation of addition products. 

Directions. — Dissolve the butter-fat in the 300-c.c. bottles 
in 10 c.c. of dry chloroform. Add 30 c.c. — in the case of a 
doubtful butter 50 c.c. — of the iodo-mercuric solution from 
a pipette or glass-stoppered burette, and allow the bottles to 



176 AIR, WATER, AND FOOD. 

stand, with frequent shaking, for three hours in a dark closet. 
A blank should be carried through at the same time and with 
the same amount of reagents, in order to determine the rela- 
tion between the thiosulphate and the iodo-mercuric solu- 
tion, the latter being liable to change. Now add 20 c.c. of 
potassium iodide (to prevent precipitation of mercuric iodide 
on dilution), then 100 c.c. of distilled water, and titrate the 

N 
excess of iodine with — sodium thiosulphate until the solu- 
tion is faintly yellow. Add a few drops of starch solution 
and titrate to the disappearance of the blue color. Calculate 
the result in grams of iodine absorbed by 100 grams of fat. 
This is called the Hubl or Iodine absorption-number. 

Standardisation of the Thiosulphate Solution. — As this is 
not permanent, its strength should be determined by means 
of the standard potassium bichromate solution, 1 c.c. of 
which is equivalent to 0.01 gram of iodine. The standardi- 
zation may be done while waiting for the absorption of the 
iodine. 

Measure 20 c.c. of the potassium bichromate from a pipette 
into an Erlenmeyer flask. Add 10 c.c. of potassium iodide, 
100 c.c. of water, and 5 c.c. of strong hydrochloric acid, and 
shake the flask for three minutes. Titrate the liberated 
iodine with the thiosulphate solution until the color has 
almost disappeared, then add starch solution and continue the 
titration until the blue color changes to a sea-green, due to 
the formation of chromium chloride. The iodine is liberated 
in accordance with the following equation: 

K,Cr 2 7 + 14HCI + 6KI = 8KC1 + 2CrCl 3 + y¥L 2 + 61. 

Calculation of Results. — Example. — From the standardi- 
zation, 



food: analytical methods: butter. 177 

17.2 c.c. thiosulphate = 2 1 . 5 c.c. bichromate = 0.2 1 5 gram I ; 

1 c.c. thiosulphate = 0.0125 gram I. 

Also, from blank, 

31 c.c. iodine solution = 46.5 c.c. thiosulphate; 
1 c.c. iodine solution = 1.5 c.c. thiosulphate. 

If 31 c.c. iodine solution have been added to 1.049 grams 

of fat, then 31.0 X 1.5 = 46.5 c.c. is the equivalent amount 

of thiosulphate solution; and if 19.4 c.c. thiosulphate were 

used to titrate excess of free iodine, 46.5 — 19.4 = 27.1 c.c. is 

the amount of thiosulphate equivalent to the iodine combined 

with the fat. Then, since 1 c.c. thiosulphate is equivalent to 

, . ,. 27.1 X 0.0125 . . 
0.0125 gram free iodine, — X 100 = 32.29 grams 

of iodine combined with 100 grams fat. 

Notes. — It is assumed that 100 grams of pure butter- fat 
absorb 30-40 grams iodine; artificial butter, 55 grams; oleo- 
margarine, 63-75 grams; olive-oil, 83 grams; and cottonseed- 
oil, 106 grams. 

The products formed by the action of iodine on the fats 
are mainly addition products with a slight proportion of sub- 
stituted bodies. Thus the unsaturated olein, (C 17 H 33 COO) 3 
C 3 H 5 , takes up six atoms of iodine, forming an addition 
product, di-iodo-stearin, (C 17 H 33 I 2 COO) 3 C 3 H 5 . 

The exact amount of iodine absorbed depends on the 
strength and the amount of iodine solution used, and on the 
length of time it is allowed to act. The presence of mer- 
curic chloride shortens the time of reaction, probably by 
acting as a carrier of iodine. 

Physical Methods. — Microscopic Examination. — Pure, 
fresh butter is not ordinarily crystalline in structure. Butter 
which has been melted, however, and fats which have been 
liquefied and allowed to cool slowly show a distinct crystal- 
line structure, especially by polarized light. If only fresh but- 



178 AIR, WATER, AND FOOD. 

ter were sold, and all adulterants had been previously melted 
and slowly cooled, this method would be all that would be 
necessary for the detection of adulteration. As it is, how- 
ever, it is most useful in making comparative examina- 
tions of samples which have been subjected to the same 
conditions. From an examination of the accompanying 
plate,* which shows the appearance by polarized light of 
four samples of known origin which were melted and cooled 
slowly under exactly similar conditions, it will be seen that, 
while the differences are noticeable, they are not sufficient in 
all cases to form a basis for absolute identification. 

For a further discussion of this point the student is re- 
ferred to Bulletin 13, U. S. Dept. Agr., Part I, pp. 29-40; 
Part IV, pp. 449-455- 

Specific Gravity. — This is most conveniently determined 
at ioo° C. by means of the Westphal balance (see Allen, The 
Analyst, 11, 223; also Bull 13, Part IV, pp. 430-431). The 
pyknometer method is, however, the one adopted by the As- 
sociation of Official Agricultural Chemists, to whose report 
(Bulletin 46, Rev. Ed., 1899, p. 51) reference is made. 

Melting-point. — This is best determined according to the 
directions given in the Bulletin just mentioned (46), p. 52. 

Refractive Index. — The degree to which light is refracted 
differs with various fats, and these differences are often of 
considerable analytical value. See Bulletin 46, Rev. Ed., p. 
49, for a description of the method employed in its determina- 
tion. 

Determination of Water. — Directions. — Weigh 2 
grams of butter into a shallow platinum dish having a flat 
bottom two inches in diameter and containing a slender stir- 
ring-rod two and a half inches long. Heat the butter in the 
oven at ioo° C. for thirty minutes, cool in a desiccator, and 

* From photomicrographs by A. G. Woodman and A. I. Kendall, 1900. 




A. Butter X 30. 

C. Oleomargarine X 30. 



B. Beef-fat X 30 
D. Lard X 30. 



food: analytical methods: butter. i8i 

weigh. Heat again for periods of fifteen minutes, until the 
weight remains constant. During the process of heating 
stir the butter frequently to hasten evaporation of the water. 

Note. — The loss in weight is calculated as water, although 
a portion of the volatile acids is also lost, the amount depend- 
ing upon the time of heating. 

Determination of Salt. — Directions. — Weigh 10 grams 

of butter in a small beaker, add 30 c.c. of hot water, and 

when the fat is completely melted transfer the whole to a 

separatory funnel. Shake the mixture thoroughly, allow 

the fat to rise to the top, and draw off the water, taking care 

that none of the fat-globules pass the stopcock. Repeat the 

operation four times, using 30 c.c. of water each time. Make 

the washings up to 250 c.c, mix thoroughly, and titrate 25 

N 
c.c. in a six-inch porcelain dish, using — silver nitrate with 

potassium chromate as an indicator. 

Complete Analysis of Butter in One Sample. — Direc- 
tions. — Weigh about 2 grams of butter into a platinum 
Gooch crucible, half-filled with ignited fibrous asbestos, and 
dry it at ioo° C. to constant weight. The loss in weight is 
the amount of water. Then treat the crucible repeatedly 
with small portions of petroleum ether, using gentle suction, 
and again dry it to constant weight. The difference between 
this and the preceding weight will be the amount of fat. 
Now carefully heat the crucible over a small flame or in a 
muffle until a light grayish ash is obtained. The loss in 
weight is the amount of curd, and the residual increase in 
weight over that of the crucible and asbestos is the ash. If de- 
sired, the salt may be washed out of the ash and determined 
by titration with silver nitrate. 

Detection of Coloring - matters. — The principal co'or- 
ing-matter used in butter is annatto; sometimes saffron is 



1 82 AIR, WATER, AND FOOD. 

employed. These may be detected by the method proposed 
by Cornwall.* 

Directions. — Dissolve about 5 grams of the warm filtered 
fat in 50 c.c. of ether and shake in a separatory funnel for 
ten or fifteen seconds with 15 c.c. of a very dilute solution 
of caustic potash, only alkaline enough to give a distinct re- 
action with turmeric-paper. After an hour or two draw off 
the aqueous solution, colored more or less by the annatto, 
shake it once more with a fresh portion of ether, and evapo- 
rate to dryness. Treat the dry residue with a drop of con- 
centrated sulphuric acid. In the presence of annatto the 
yellow residue turns blue or violet, then quickly green, and 
finally brownish or somewhat violet. Saffron differs in not 
giving the green coloration. Blank tests should be made 
with the ether. 

FLOUR, PREPARED CEREALS, ETC. 

This class of foodstuffs is usually in a dry form and not 
liable to rapid change by micro-organisms, and the examina- 
tion consists in the determination of their " food value." This 
may require a simple analytical process, as in the case of the 
quantity of nitrogen in a sample of " gluten " sold for diabetic 
patients, or in the case of a brand of flour to be used in a hos- 
pital or State institution. It may also require an estimation 
of the available food-material, as in the case of two kinds of 
beans or corn. The actual determination of digestibility be- 
longs to physiological chemistry and need not be taken into 
consideration here. 

Moisture. — Directions. — Spread about 2 grams of the 
finely ground material in a thin layer on a watch-glass and 
dry it in the oven at ioo° C. for five hours. 

* Chem. News, 55 {1887), 49. 



food: analytical methods: cereals. 183 

Note. — With some substances drying in a current of 
hydrogen or some inert gas may be necessary, but for most 
cereals the method given will be found satisfactory. 

Ash. — Directions. — Weigh about 2 grams into a plati- 
num dish, such as is used for the determination of water in 
butter, and char it carefully. Ignite at a very low red heat 
until the ash is white, preferably in a muffle or radiator. 

Note. — If a white ash cannot be obtained in this manner, 
exhaust the charred mass with water, collect the insoluble 
residue on a filter, burn it, add this ash to the residue from 
the evaporation of the aqueous extract and heat the whole at 
a low red heat until the ash is white. 

Ether Extract : Fats and Oils. — Directions. — Place the 
residue from the determination of moisture, as described 
above, in an extraction-cone and extract it with pure anhy- 
drous ether for sixteen hours. Evaporate off the ether and 
dry the residual fat at a low temperature to constant weight. 

Total Proteids : Determination of Nitrogen by the 
Kjeldahl Process.* — Principle. — Oxidation of carbon and 
hydrogen, and conversion of organic nitrogen to ammonium 
sulphate by means of boiling sulphuric acid in presence of 
mercury, the latter acting as a carrier of oxygen, and being 
converted to mercuric sulphate. Precipitation of mercury by 
potassium sulphide to prevent the formation of mercur- 
ammonium compounds when the solution is made alkaline. 
Setting free of ammonia by neutralization of the acid by po- 
tassium hydroxide. Distillation of ammonia into a measured 

N 
quantity of — hydrochloric acid. Titration of excess of acid. 

Directions. — Transfer about 0.5 gram of the finely divided 
substance from a weighing-tube to a 750-c.c. round-bot- 
tomed flask, add 10 c.c. of concentrated sulphuric acid free 

* Ztschr. anal. Chem., 22 {1883), 366. 



1 84 AIR, WATER, AND FOOD. 

from nitrogen, and 0.2 gram of metallic mercury. Place a 
small funnel in the neck of the flask, which should be sup- 
ported in an inclined position on wire gauze and heated with 
a small flame until frothing has ceased and the liquid boils 
quietly. Then increase the heat and boil the solution for half 
an hour after it becomes colorless. Allow the flask to cool 
for a minute or two, and add a few crystals of potassium per- 
manganate until the liquid has acquired a slight green or 
purple color. Meanwhile free the distilling apparatus from 
ammonia by distillation with pure water until a slight color 
only is given to 50 c.c. of the distillate by Nessler's reagent. 

N 
Measure 25 c.c. of — hydrochloric acid from a burette 

into a 300-c.c. Erlenmeyer flask and place the condenser-tip 
beneath the surface of the liquid, adding a little water, if nec- 
essary, to seal it. 

Rinse down the neck of the digestion-flask with 100 c.c. 
of ammonia-free water, add 20 c.c. of potassium sulphide 
solution, and connect the flask with the condenser. Add 100 
c.c. of caustic potash through the separatory funnel, and dis- 
til off the ammonia by steam. When 200 c.c. have distilled 
over, remove the collecting-flask, after rinsing off the conden- 
ser-tip with distilled water, and titrate the excess of acid with 

N 

— sodium hydroxide, using methyl orange or cochineal as 

indicator. A blank determination is made with 0.5 gram of 
cane-sugar in order, to reduce any nitrates present in the re- 
agents which might otherwise escape detection. 

Notes. — The temperature during the digestion must be 
maintained at or near the boiling-point of the acid, since at a 
lower temperature the formation of ammonia is incomplete. 

The process is considered by Dafert * to take place in four 

* Ztschr. anal. Chem., 24 (1885), 455. 



food: analytical methods: cereals. 185 

steps: (1) the sulphuric acid takes the elements of water from 
the organic matter; (2) the sulphur dioxide produced by the 
action of the residual carbon on the sulphuric acid exercises 
a reducing action on the nitrogenous bodies; (3) the nitro- 
genous substances formed in this way are converted to am- 
monia by a process of oxidation; (4) the ammonia formed is 
fixed by the acid as ammonium sulphate. 

In some cases the potassium permanganate is necessary 
to insure the complete conversion of the nitrogenous bodies 
into ammonia, although it is probable that its use is unneces- 
sary in the majority of analyses. 

The Kjeldahl process in the form outlined above is not 
applicable to the determination of nitrogen in the form of 
nitrates. In order to render it of more general application 
various modifications of the method have been proposed, the 
one generally used in this country being that suggested by 
Scovell.* In this method salicylic acid is used with the sul- 
phuric acid, being converted by the nitrate into nitro-phenol. 
By the use of sodium thiosulphate or zinc-dust this is reduced 
to amido-phenol. The amido-phenol is transformed into am- 
monium sulphate by the heating with sulphuric acid, the use 
of mercury being absolutely necessary in this case to secure 
the complete transformation. 

The per cent, of proteids may be found by multiplying the 
per cent, of nitrogen by an appropriate factor, the one in gen- 
eral use being 6.25. It is better to use a special factor for each 
cereal, however, using the factor 6.25 only when a special fac- 
tor is not given. The factors for the common cereals are: 
wheat 5.70, rye 5.62, oats 6.31, maize 6.39, and barley 5.82. 

Qualitative Tests for Proteids. — (a) Biuret Reaction. 
— To a small quantity of the solution add about 1 c.c. of di- 

* U. S. Dept. Agr., Bull. 16 (1887), 51. 



1 86 AIR, WATER, AND FOOD. 

lute (4 per cent.) copper sulphate solution and then a consid- 
erable excess of strong caustic potash or soda. A violet color 
is produced. The test is generally known as the biuret reac- 
tion because the substance biuret, C 2 H 6 N 3 02, left on heating 
urea to 160 C, gives the color under the same conditions. If 
too much of the copper sulphate solution be used, its color 
may conceal that of the reaction. 

(b) Xanthoproteic Reaction. — Strong nitric acid produces a 
yellow coloration of proteid matter, which is intensified on 
warming. On treating the yellow mixture with ammonia in 
slight excess the color is changed to an orange or red tint. 

(c) Milton's Reaction. — When proteid matter is boiled 
with Millon's reagent (see page 211), a brick-red coloration is 
produced. A similar reaction is given by gelatin and allied 
bodies. 

(d) Liebermann 's Test. — Heat the solid proteid with con- 
centrated hydrochloric acid. It will dissolve with the gradual 
formation of a blue coloration, changing to violet and brown. 

(e) Adamkiewicz Reaction. — If glacial acetic acid in. excess 
and then strong sulphuric acid are added to a proteid, a vio- 
let color with faint fluorescence is produced. 

Note. — Since many other substances give a test with cer- 
tain of the reagents employed to test for proteids, it will be 
obvious that a proteid can be identified with certainty only by 
employing a large number of its reactions. 

Separation of the Proteids of Wheat. — As an ex- 
ample of the principles involved in the separation of vegetable 
proteids may be taken the separation of the proteids of wheat. 
The principal proteids found in wheat are glntenin, gliadin y 
edestin, and lencosin. There is also present in wheat a certain 
amount of nitrogen in the form of amides, and a trace 
of lecithin, a nitrogenous body allied to the fats. The total 
proteid matter insoluble in cold water is ordinarily known as 



food: analytical methods: cereals. 187 

gluten. It is a mixture of the two proteids first named. The 
crude gluten is readily obtained from flour by kneading a 
quantity of it in a thin stream of cold water until the starch 
and soluble matter is removed. 

The methods of separation depend in general upon the 
relative solubility of the proteids in dilute salt solutions or in 
alcohol of different strengths.* 

Edestin and Lencosin. — These may be determined together 
by first extracting a definite weight of the finely ground ma- 
terial with a 1 per cent, sodium chloride solution. To an 
aliquot part of the clear salt solution is added sufficient strong 
alcohol to make the mixture 75 per cent, alcohol. After 
standing overnight the precipitate is filtered off and the nitro- 
gen in it determined. If desired, the two proteids may be 
separated by coagulating the leucosin at 6o° C. and precipi- 
tating the edestin by adding alcohol to the clear filtrate as 
before. The nitrogen in each precipitate is then determined. 

Amides. — Determined by precipitating all the proteids 
from the above salt solution by means of phospho-tungstic 
acid. After standing overnight the precipitated proteids are 
filtered off and the nitrogen of the amides in the solution de- 
termined. 

Gliadin. — About a gram of the finely divided material is 
extracted with hot alcohol (sp. gr. 0.90). The filtrate and 
washings are evaporated to dryness in a Kjeldahl flask and 
the nitrogen determined in the residue. The per cent, of 
nitrogen found, less the per cent, of amide nitrogen, is the per 
cent, of gliadin nitrogen. 

Glutenin. — This is the difference between the per cent, of 
total nitrogen and the per cents, of the edestin, leucosin, 
gliadin, and amide nitrogen. 

* G. L.Teller: Ark. Agr. Expt. Sta., Bull. 42 {1896), 81: see also 
Osborne's papers in Am. Chem. J. y 13-15. 



1 88 AIR, WATER, AND FOOD. 

The per cents, of the various proteids may be found by 
multiplying the corresponding nitrogen by 5.70. 

Carbohydrates. — Total Carbohydrates. — Generally deter- 
mined by subtracting from 100 the sum of the per cents, of 
the other constituents, viz., water, ash, fats and oils, and nitro- 
genous matters. The total carbohydrates are made up princi- 
pally of sugars, starches, and crude fibre, the latter including 
pentosans and cellulose. 

Sugars. — The finely ground material, previously ex- 
tracted with petroleum ether if much oil is present, is ex- 
tracted for about three hours with 80 per cent, alcohol. The 
extracted matter is dried at a low temperature and weighed. 

Starch. — The methods for the determination of starch 
vary with the condition in which the starch is found. In the 
case of nearly pure starch it may be converted into dextrose 
by boiling with dilute acid, the dextrose being then deter- 
mined by Fehling's solution in the usual way. Hot acids, 
however, cannot be used to convert starch in the natural state, 
as it is found in cereals, because other carbohydrate bodies 
become soluble under these conditions. In such cases the 
starch is brought into solution by treatment with diastase or 
by heating with water under pressure. 

For the rapid estimation of starch in cereals the following 
method has been found useful: * 

Principle. — Conversion of starch to dextrin and maltose, 
that is, solution of the starch by diastase in malt extract. Con- 
version of dextrin and maltose to dextrose by acid (hy- 
drolysis). 

Directions. — Place about a gram of the finely divided sam- 
ple, the residue from the extraction of sugar, for example, in 
a flask, add 50 c.c. of water, 3 ex. of malt extract, and boil for 

* Hibbard: /. Am. Chem. Soc, 17 {i8gs), 64. 



food: analytical methods: cereals. 189 

one minute, with frequent shaking. Cool the solution to 
6o° C, add 3 c.c. of malt extract, and heat slowly so that 
fifteen minutes are required to reach the boiling-point. Test 
the solution for starch by placing a drop upon a porcelain tile 
and adding a drop of solution of iodine in potassium iodide. 
Should a blue color appear, add more malt extract and repeat 
the heating until all the starch has been converted. Cool the 
solution, make it up to 100 c.c, and filter it through fine linen 
or cotton cloth. To an aliquot part of the filtrate, 25 or 50 
c.c, in a flask, add 5 c.c. of hydrochloric acid (sp. gr. 1.15), 
and enough water to make the volume 60 c.c. Place a small 
funnel in the neck of the flask to retard evaporation and boil 
the solution gently for exactly half an hour. Cool the solu- 
tion, add sodium hydroxide until nearly neutralized, and de- 
termine the dextrose by Fehling's solution. A blank deter- 
mination should be carried through under the same conditions 
and using the same quantities of reagents, in order to make a 
correction for the sugar in the malt extract. 

Malt Extract. — Treat coarsely pulverized dry malt for sev- 
eral hours with sufficient 20 per cent, alcohol to cover it. The 
solution is then filtered and may be kept for two weeks with- 
out losing its diastatic power. 

If the malt itself is not readily procurable, certain forms of 
prepared diastase are on the market and may be found more 
convenient either for analytical use or for purposes of illus- 
tration. When possible, however, it is preferable to use the 
freshly prepared malt extract as the prepared diastase, made 
at different times and from separate portions of malt, may 
show great differences in hydrolytic power. 

Crude Fibre- — This may be determined by the method 
adopted by the Association of Official Agricultural Chemists.* 

* U. S. Dept. Agr., Div. of Chem., Bull. 46 [Rev. Ed.] (1S9S), 26. 



190 AIR, WATER, AND FOOD. 

EXAMINATION OF FERMENTED LIQUORS. 
WINE. 

Effervescing wines should, before analysis, be vigorously 
shaken in a large flask, to remove carbon dioxide. 

Specific Gravity. — This is to be taken by means of the 
Westphal balance or Sprengel tube at 15. °5 C. 

Alcohol by Weight. — Principle. — The alcohol is ob- 
tained freed from everything but water and its amount deter- 
mined by ascertaining the specific gravity of the mixture, and 
taking the per cent, from tables. 

Directions. — Weigh out about 50 c.c. of the wine in a small 

flask and transfer it with 100 c.c. of water to a 500-c.c. round- 

N 
bottomed distilling-flask. Neutralize free acid with — sodium 

hydroxide and add 0.5 gram of tannin, if necessary, to pre- 
vent frothing. Distil off about 100 c.c. into a 150-c.c. tared 
flask which should be provided with a cork, perforated to re- 
ceive the condenser-tip, and carrying a mercury-valve to pre- 
vent loss of alcohol. Weigh the distillate, mix it thoroughly, 
and take its specific gravity at I5.°5 C. with a pyknometer. 
The percentage of absolute alcohol by weight corresponding 
to the observed density will be found in Table X, page 203. 

Example. — If A is the percentage of absolute alcohol in 
the sample, a that in the distillate, W and w the weights of 

wa 
the sample and distillate respectively, then A = 7^. 

Notes. — If the specific gravity of the wine is known, 
weighing may be avoided by carefully measuring both sample 
and distillate at i5-°5 C. The corresponding percentage of 
alcohol by volume may be found by appropriate tables. (See 
Sadtler's Industrial Organic Chemistry.) 

In the case of distilled liquors about 30 grams are diluted 



FOOD: ANALYTICAL- METHODS: FERMENTED LIQUORS. I9I 

to 150 c.c, 100 c.c. distilled, and the per cent, of alcohol by 
weight determined as above. 

The object of neutralizing the wine with sodium hydrox- 
ide is to prevent the distillation of volatile acids, principally 
acetic. A certain amount of volatile ethers may also pass 
over into the distillate, but in most cases it is so slight that its 
influence may be neglected. 

Extract. — Dry Wines. — Weigh out about 50 c.c. in a 
small flask, transfer to a platinum dish having a flat bottom, 
and evaporate on the water-bath to the consistency of syrup. 
Then heat the residue in the oven at ioo° C. for two hours 
and a half, cool in a desiccator, and weigh. 

Sweet Wines. — Weigh out 10 c.c, dilute to 100 c.c, and 
evaporate 50 c.c as directed above. 

Notes. — The extract is composed mainly of dextrins, 
sugars, organic acids, nitrogenous substances, and mineral 
matters. Of these the dextrins and sugars form the chief 
part, the proteids, however, amounting to about ten per cent, 
in the case of beer made from malt. 

Ash. — Ignite the extract at a very low red heat. 

Free Acids: Total Acidity Calculated as Tartaric 

N 
Acid. — Titrate 10 c.c of the wine with — sodium hydroxide. 

10 J 

The end-point is reached when a drop of the liquid placed 

upon faintly-red litmus paper produces a blue spot in the 

middle of the portion moistened. Calculate the results as 

N . 

tartaric acid. One c.c — sodium hydroxide — 0.0075 gram 

of tartaric acid. 

Volatile Acids Calculated as Acetic Acid- — Measure 
50 c.c. of wine into a 300-cc flask provided with a cork hav- 
ing two perforations. One is fitted with a tube 6 mm. in 
diameter and blown out to a bulb 40 mm. in diameter a short 



192 AIR, WATER, AND FOOD. 

distance above the cork; this tube is connected with a con- 
denser. The other perforation carries a tube reaching nearly 
to the bottom of the flask and drawn out to a small aperture 
at its lower end; this is connected with a 500-c.c. flask con- 
taining water. Heat both flasks to boiling; then lower the 
flame under that containing the wine and continue the distil- 
lation by means of steam until 200 c.c. have gone over. Tit- 

N 
rate the distillate with — sodium hydroxide, using phenolph- 

thalein as an indicator. Calculate the results as acetic acid. 

N 
One c.c. — sodium hydroxide == 0.0060 gram of acetic acid. 

Fixed Acids Calculated as Tartaric Acid. — These 
may be found by calculating the volatile acids as tartaric and 
subtracting the result from the total tartaric acid found by 
direct titration. 

Coloring Matters. — The various aniline colors are gen- 
erally used in artificially colored wines, the color most com- 
monly occurring being fuchsine. 

Cazeneuve Reaction. — Add 0.2 gram of precipitated mer- 
curic oxide to 10 c.c. of the wine, shake for one minute and 
filter. Pure wines give a filtrate which is colorless or light 
yellow, while the presence of a more or less red coloration in- 
dicates the presence of an aniline color. 

Detection of Fuchsine and Orseille. — To 20 c.c. of wine add 
10 c.c. of basic lead acetate solution, heat slightly, and mix 
by shaking. Filter into a test-tube, add 2 c.c. of amyl alco- 
hol, and shake. If the amyl alcohol be, colored red, separate 
it and divide it into two portions. To one add hydrochloric 
acid, to the other ammonia. If the color is due to fuchsine, 
the amyl alcohol will be decolorized in each case; if due to 
orseille, the ammonia will change the color of the amyl alco- 
hol to purplish violet. 



food: analytical methods: fermented liquors. 193 

Detection of Salicylic Acid. — Spica's Method. — Acidify 
100 c.c. of the wine with sulphuric acid and extract with ether. 
Evaporate the extract to dryness, warm the residue carefully 
with one drop of concentrated nitric acid and add two or 
three drops of ammonia. The presence of salicylic acid is in- 
dicated by the formation of a yellow color, due to ammonium 
picrate, and may be confirmed by immersing a thread of fat- 
free wool, which will be dyed a permanent yellow. 

Guard's Method. — Extract a portion of the acidified liquor 
with ether as in the preceding method, evaporate the extract 
to dryness, and extract the residue with petroleum ether. 
Evaporate the petroleum ether extract, dissolve the residue 
in water and add a few drops of a very dilute solution of ferric 
chloride. A violet-red color indicates salicylic acid. 

Beer and Other Malt Liquors. — Before analysis the 
sample must be thoroughly shaken in a large flask, in order 
to remove carbon dioxide. 

Specific Gravity. — Taken with a pyknometer or Sprengel 
tube at 15. °5 C. 

Alcohol by Weight. — Determined as in the analysis of wine, 
using 100 c.c. of the sample and 50 c.c. of distilled water. 

Extract and Ash. — Determined as in the analysis of dry 
wines. 

Free Acids. — Titrated as in the analysis of wine. Fixed 
acids, consisting principally of lactic and succinic, are calcu- 
lated as lactic acid. Volatile acids are calculated as acetic 

N 
acid. One c.c. of — sodium hydroxide = 0.0090 gram of 

lactic acid. 

Nitrogen. — Weigh out about 20 c.c. of the sample, transfer 
it to a 750-c.c. round-bottomed flask, and evaporate almost 
to dryness on the water-bath. Determine the nitrogen in the 
residue as on page 92. 



APPENDIX A. 



Table I. 

TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY FROM 
0° TO 30°.9 C, REDUCED TO 0° AND SEA-LEVEL. 





o°.o. 


o°.i. 


0°.2. 


o°. 3 - 


o°. 4 - 


00.5. 


o°.6. 


o°. 7 . 


o°.8. 


o°. 9 . 


0° 


4-57 


4.60 


4.64 


4.67 


4-70 


4-74 


4-77 


4.80 


4.84 


4.87 


I 


4.91 


4.94 


4.98 


5.02 


5.05 


5-09 


5-12 


5.16 


5-20 


5.23 


2 


5.27 


5-31 


5-35 


5-39 


5.42 


5-46 


5.50 


5.54 


5.58 


5.62 


3 


5-66 


5-70 


5-74 


5-78 


5.82 


5.86 


5.90 


5-94 


5-99 


6.03 


4 


6.07 


6. 11 


6.15 


6.20 


6.24 


6.28 


6-33 


6-37 


6.42 


6.46 


5 


6.51 


6.55 


6.60 


6.64 


6.69 


6.74 


6.78 


6.83 


6.88 


6.92 


6 


6.97 


7.02 


7.07 


7.12 


7.17 


7.22 


7.26 


7.3i 


7-36 


7.42 


7 


7-47 


7.52 


7-57 


7.62 


7.67 


7.72 


7-78 


7.83 


7.88 


7-94 


8 


7-99 


8.05 


8.10 


8.15 


8.21 


8.27 


8.32 


8.38 


8-43 


8-49 


9 


8-55 


8.61 


8.66 


8.72 


8.78 


8.84 


8.90 


8.96 


9.02 


9.08 


10 


9.14 


9.20 


9.26 


9-32 


9.39 


9-45 


9-5i 


9.58 


9.64 


9.70 


ii 


9-77 


9-83 


9.90 


9.96 


10.03 


10.09 


10.16 


10.23 


10.30 


IO.36 


12 


10.43 


10.50 


10.57 


10.64 


10.71 


10.78 


10.85 


10.92 


10.99 


II.06 


13 


11. 14 


11. 21 


11.28 


11.36 


I i-43 


11.50 


11.58 


11.66 


H-73 


II. 8l 


14 


11.88 


11.96 


12.04 


12.12 


12. 19 


12.27 


12.35 


12.43 


12.51 


12.59 


15 


12.67 


12.76 


12.84 


12.92 


13.00 


13.09 


13.17 


13-25 


13.34 


13.42 


16 


I3-5I 


13.60 


13.68 


13-77 


13.86 


13-95 


14.04 


14.12 


14.21 


I4.3O 


17 


14.40 


14.49 


14.58 


14.67 


14.76 


14.86 


14-95 


15.04 


15.14 


15-23 


18 


15.33 


15-43 


15-52 


15.62 


15.72 


15.82 


15.92 


16.02 


16.12 


16.22 


19 


16.32 


16.42 


16.52 


16.63 


16.73 


16.83 


16.94 


17.04 


17.15 


17.26 


20 


17.36 


17-47 


17.58 


17.69 


17.80 


17.91 


18.02 


18.13 


18.24 


18.35 


21 


18.47 


18.58 


18.69 


18.81 


18.92 


19.04 


19.16 


19.27 


19-39 


19.51 


22 


19.63 


19-75 


19.87 


19.99 


20.11 


20.24 


20.36 


20.48 


20.61 


20.73 


23 


20.86 


20.98 


2i.11 


21 .24 


21.37 


21.50 


21.63 


21.76 


21.89 


22.02 


24 


22.15 


22.29 


22.42 


22.55 


22.69 


22.83 


22.96 


23.10 


23-24 


23-38 


25 


23.52 


23.66 


23.80 


23-94 


24.08 


24-23 


24.37 


24.52 


24.66 


24. Si 


26 


24.96 


25.10 


25.25 


25.40 


25o5 


25.70 


25.86 


26.01 


26.16 


26.32 


27 


26.47 


26.63 


26.78 


26.94 


27.10 


27.26 


27.42 


27.58 


27.74 


27.90 


28 


28.07 


28.23 


28.39 


28.56 


28.73 


28.89 


29.06 


29.23 


29.40 


29-57 


29 


29.74 


29.92 


30.09 


30.26 


30.44 


30.62 


30.79 


30.97 


3I.I5 


31.33 


30 


3i-5i 


31.69 


31-87 


32.06 


32.24 


32.43 


32.61 


32.80 


32.99 


33.18 



195 



196 



APPENDIX A. 



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APPENDIX A. 



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APPENDIX A. 



199 



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APPENDIX A. 
Table VII. 



TABLE OF HARDNESS, SHOWING THE PARTS OF CALCIUM CAR- 
BONATE (CaCO s ) IN 1,000,000 FOR EACH TENTH OF A CUBIC 
CENTIMETER OF SOAP SOLUTION USED. 





0.0 


0.1 


0.2 


0.3 


0.4 


0.5 


0.6 


0.7 


0.8 


0.9 




cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


0.0 
















0.0 


1.6 


3-2 


1.0 


4.8 


6.3 


7-9 


9-5 


II. I 


12.7 


14-3 


15.6 


16.9 


18.2 


2.0 


19-5 


20.8 


22.1 


23.4 


24.7 


26.O 


27-3 


28.6 


29.9 


31.2 


3-0 


32.5 


33-8 


35-1 


36.4 


37.7 


39-o 


40.3 


41.6 


42.9 


44-3 


4.0 


45-7 


47-1 


48.6 


50.0 


51.4 


52.9 


54-3 


55-7 


57.1 


58.6 


5-0 


60.0 


61.4 


62.9 


64.3 


65.7 


67.1 


68.6 


70.0 


71.4 


72.9 


6.0 


74-3 


75-7 


77-1 


78.6 


80.O 


81.4 


82.9 


84-3 


85-7 


87.1 


7.0 


88.6 


90.0 


9I.4 


92.9 


94-3 


95-7 


97.1 


98.6 


100. 


101.5 


8.0 


103.0 


104.5 


I06.0 


107 -5 


109.0 


no. 5 


112. 


II3-5 


1150 


116. 5 


9.0 


118. 


H9-5 


121. I 


122.6 


124. 1 


125.6 


127. 1 


128.6 


130. 1 


131-6 


10. 


I33-I 


134.6 


I36. I 


137-6 


I39-I 


140.6 


142. 1 


143-7 


145.2 


146.8 


11 .0 


148.4 


150.0 


I5T-6 


153.2 


154-8 


156.3 


157-9 


159-5 


161. 1 


162.7 


12.0 


164.3 


165.9 


167.5 


169.0 


170.6 


172.2 


173-8 


175-4 


177.0 


178.6 


13-0 


180.2 


181. 7 


183-3 


184.9 


186.5 


188. 1 


189.7 


I9I-3 


192.9 


194.4 


14.0 


196.0 


197.6 


199.2 


200.8 


202.4 


204.0 


205.6 


207.1 


208.7 


210.3 


15.0 


211. 9 


213.5 


215. 1 


216.8 


218.5 


220.2 


221.8 


223.5 


225.2 


226.9 



Table VIII. 

SHOWING THE NUMBER OF CUBIC CENTIMETERS OF OXYGEN DIS- 
SOLVED IN IOOO CUBIC CENTIMETERS OF WATER WHEN 
SATURATED AT DIFFERENT TEMPERATURES, AS CAL- 
CULATED BY WINKLER.* 



Deg. Cent. 


Cu. Cm. 


Deg. Cent. 


Cu. Cm. 


Deg. Cent. 


Cu. Cm. 


O 


IO.187 


II 


7.692 


21 


6.233 


I 


9.910 


12 


7.518 


22 


6. 114 





9-643 


13 


7.352 


23 


5-999 


3 


9-387 


14 


7.192 


24 


5.886 


4 


9.142 


15 


7.038 


25 


5.776 


5 


8.907 


16 


6.89I 


26 


5669 


6 


8.682 


17 


6.750 


27 


5.564 


7 


8.467 


18 


6.614 


28 


5. 460 


8 


8.260 


19 


6.482 


29 


5-357 


9 


8.063 


20 


6.356 


30 


5.255 


10 


7.873 











Berichte, 22 {188 '9), 1772. 



APPENDIX A. 20 1 

Table IX. 

FOR CORRECTING THE SPECIFIC GRAVITY OF MILK ACCORDING TO 
TEMPERATURE. ADAPTED FROM THE TABLE OF VIETH. 

(Temperature in Degrees Centigrade.) 



Specific 
Gravity. 


:o° 


ii° 


12° 


13° 


14° 


15° 


1 6° 


i 7 ° 


18 


i 9 ° 


20° 


1.025 


24.I 


24-3 


24.5 


24.6 


24.7 


24.9 


25.1 


25.3 


25-4 


25. b 25.9 


26 


25.1 


25.2 


25-4 


25-5 


25-7 


25.9 


26.1 


26.3 


26 


5 


2b. 7; 27.0 


27 


26.1 


26.2 


26.4 


26.5 


26.7 


26.9 


27.I 


27.4 


27 


5 


27.7 


28.0 


28 


27.0 


27.2 


27.4 


27.5 


27.7 


27.9 


28.1 


28.4 


28 


5 


28.7 


29.0 


29 


28.0 


28.2 


28.4 


28.5 


28.7 


28.9 


29.I 


29.4 


29 


5 


29.8 30.1 


30 


29.O 


29. 1 


29-3 


29-5 


29.7 


29.9 


30.1 


30.4 


30 


5 


30.8 31. 1 


31 


29.9 


30. 1 


30.3 


30.4 


30.6 


30.9 


31.2 


31-4 


3i 


5 


31.8 32.2 


32 


30.9 


3I-I 


3i-3 


3i-4 


31.6 


3i-9 


32.2 


32.4 


32 


b 


32.9 


33-2 


33 


31.8 


32.0 


32.3 


32.4 


32.6 


32-9 


33-2 


33-4 


33 


6 


33-9 


34-2 


34 


32.7 


33.o 


33-2 


33-4 


33-6 


33-9 


34-2 


34-4 


34 


b 


34-9 


35-2 


35 


33-6 


33-9 


34-1 


34-4 


34-6 


34-9 


35-2 


35-4 


35-6 


35-9 


36.2 



Directions. — Find the observed gravity in the left-hand column. Then 
in the same line, and under the observed temperature, will be found the 
corrected reading. 



202 



APPENDIX A. 



Table X. 



PERCENTAGE OF ALCOHOL BY WEIGHT FROM THE SPECIFIC GRAVITY 







AT I 


5°-5 c 


(hehner.) 








Per cent. 




Per pent. 




Per cent. 




Per cent. 


Sp. Gr. 


Alcohol 


Sp. Gr. 


Alcohol 


Sp. Gr. 


Alcohol 


Sp. Gr. 


Alcohol 


15.5 L. 


by 


i5°.5 C. 


by 


I5°-5C. 


by 


i5°-5 C. 


by 




Weight. 




Weight. 




Weight 




Weight. 


I. 0000 


0.00 


7 


2.44 


4 


5.00 


I 


7.87 






6 


2.50 


3 


5.06 


O 


7-93 


0.9999 

8 

7 
6 


0.05 

0. II 
0. 16 

0.21 


5 
4 
3 


2.56 
2.6l 
2.67 


2 

I 



5-12 
5-19 
5.25 


O.9869 

8 
7 


8.00 

8.07 
8.14 


5 


O.26 


2 
1 


2. 72 
2.78 
2.83 


0.9909 


5-3i 


6 


8.21 


4 


O.32 





8 


5-37 


5 


8.29 


3 


0.37 


7 


5-44 


4 


8.36 


2 


O.42 


O.9949 


2.89 


6 


5-50 


3 


8-43 


1 


0.47 


8 


2.94 


5 


5.56 


2 


8.50 





Oo3 


7 


3.OO 


4 


5.62 


1 


8.57 


O.9989 

8 

7 
6 


O.58 

O.63 
O.68 
O.74 


6 
5 
4 
3 


3.06 
3-12 

3.18 
3.24 


3 
2 
1 



5-69 
5-75 
5.81 

5.87 




O.9859 

8 
7 


8.64 

8.71 

8.79 
8.86 


5 


O.79 


2 
j 


3- 2 9 

3-35 
3-4i 


O.9899 


5-94 


6 


8.93 


4 
3 


O.84 
O.89 





8 
7 


6.00 

6.07 


5 
4 


9.00 

9.07 


2 


0-95 


O.9939 


3-47 


6 


6. 14 


3 


9.14 


1 


I .00 


8 


3-53 


5 


6.21 


2 


9.21 





1.06 


7 


3-59 


4 


6.28 


1 


9.29 


O.9979 

8 
7 


I. 12 

I. 19 

1.25 


6 

5 
4 

3 


3-65 
3-7i 
3-76 
3.82 


3 
2 




6.36 

6-43 
6.50 

6-57 




O.9849 

8 


9-36 

9-43 

9-50 


6 


I- 31 




3-88 • 

3-94 
4.00 






7 


9-57 


5 


i-37 


2 


O.9889 


6.64 


6 


9.64 


4 
3 


1.44 
1.50 





8 
7 


6.71 
6.78 


5 
4 


9.71 
9-79 


2 


1.56 


O.9929 


4.06 


6 


6.86 


3 


9.86 


1 


1.62 


8 


4.12 


5 


6-93 


2 


9-93 





1.69 


7 


4.19 


4 


7.00 


1 


10.00 


O.9969 

8 
7 
6 


i-75 

1. 81 

1.87 
1.94 


6 
5 
4 
3 


4-25 

4.3i 
4-37 
4.44 


3 
2 

1 



7.07 

7-13 
7.20 

7.27 




O.9839 

8 

7 


10.08 

10. 15 

10.23 
10.31 


5 


2.00 


2 
j 


4- 50 
4-56 
4.62 


O.9879 


7-33 


6 


10.38 


4 


2.06 





8 


7.40 


5 


10.46 


3 


2. 11 




7 


7-47 


4 


10.54 


2 


2.17 


O.9919 


4.69 


6 


7-53 


3 


10.62 


1 


2.22 


8 


4-75 


5 


7.60 


2 


10.69 





2. 28 


7 


4.81 


4 


7.67 


1 


10.77 


0-9959 

8 


2.33 

2.39 


6 
5 


4.87 
4.94 


3 
2 


7-73 
7.80 



O.9829 


10.85 
10.92 



APPENDIX A. 



203 



TABLE X. — Continued. 
PERCENTAGE OF ALCOHOL BY WEIGHT. 





Per cent. 


j 


Per cent. 




Per cent. 




Per cent. 


Sp. Gr. 


Alcohol 


Sp. Gr. 


Alcohol 


Sp. Gr. 


Alcohol 


Sp. Gr. 


Alcohol 


i5°.5 C. 


by 


| i5°-5C. 


by 


i5°.5 C. 


by 


i5°.5 C. 


by 




Weight. 




Weight. 




Weight. 




Weight. 


O.9829 


IO.92 


4 


14-45 


O.9739 


I8.I5 


4 


21-77 


8 


II.OO 


3 


14-55 


8 


18.23 


3 


21.85 


7 


II.08 


2 


14.64 


7 


18.31 


2 


21.92 


6 


II. 15 


1 


14-73 


6 


18.38 


I 


22.00 


5 


11.23 





14.82 


5 


18.46 





22.08 


4 
3 
2 

1 



II. 31 

II.38 
II.46 
H-54 
11.62 


O.9779 

8 

7 
6 


14.90 

15 -OO 
15.08 
15-17 


4 

3 
2 

1 



18.54 
18.62 
18.69 

18.77 
18.85 


0.9689 

8 

7 
6 


22.15 

22.23 
22.31 

22.38 






5 


15.25 






5 


22.46 


O.9819 


11.69 


4 


15-33 


O.9729 


18.92 


4 


22-54 


8 


11.77 


3 


15.42 


8 


19.OO 


3 


22.62 


7 


11.85 


2 


15.50 


7 


19.08 


2 


22.69 


6 


11.92 


1 


15-58 


6 


19.17 


1 


22.77 


5 


12.00 





15.67 


5 


19.25 





22.85 


4 
3 
2 
1 



12.08 
12.15 
12.23 
12.31 
12.38 


O.9769 

8 

7 
6 

5 


15-75 

15-83 
15.92 
16.00 
16.08 


4 
3 
2 
1 



19.33 
19.42 
19.50 
19.58 
19.67 


O.9679 

8 

7 
6 

5 


22.92 

23.OO 
23.08 

23-15 
23.23 


O.9809 


12.46 


4 


16.15 


O.9719 


19-75 


4 


23.31 


8 


12.54 


3 


16.23 


8 


19.83 


3 


23.38 


7 


12.62 


2 


16.31 


7 


19.92 


2 


23.46 


6 


12.69 


1 


16.38 


6 


20.00 


1 


23-54 


5 


12.77 





16.46 


5 


20.08 





23.62 


4 
3 


12.85 
12.92 


0-9759 

8 


16.54 

16.62 


4 
3 


20.17 
20.25 


O.9669 

8 


2369 

23.77 


2 
1 



13.00 
13-08 
13-15 


7 
6 

5 


16.69 
16.77 

16.85 


2 
1 



20.33 
20.42 
20.50 


7 
6 

5 


23.85 
23.92 
24.00 


O.9799 


13-23 


4 


16.92 


O.9709 


20.58 


4 


24.08 


8 


13-31 


3 


17.00 


8 


20.67 


3 


24.15 


7 


13-33 


2 


17.08 


7 


20.75 


2 


24.23 


6 


13.46 


1 


17-17 


6 


20.83 


1 


24-31 


5 


13-54 





17.25 


5 


20.92 





24.38 


4 
3 
2 
1 



13.62 
13.69 
13-77 
13.85 
13.92 


O.9749 

8 

7 
6 

5 


17-33 

17.42 
17.50 
17.58 
17.67 


4 
3 
2 

1 



2I.OO 
21.08 
21.15 
21.23 
21.31 


09659 

8 

7 
6 

5 


24.46 

24-54 
24.62 
24.69 

24.77 


O.9789 


14.00 


4 


17.75 


O.9699 


21.38 


4 


24. S5 


8 


14.09 


3 


17.83 


8 


21.46 


3 


24.92 


7 


14.18 


2 


17.92 


7 


21.54 


2 


25.00 


6 


14.27 


1 


18.00 


6 


21 .62 






5 


14.36 





18.08 


5 


21.69 







APPENDIX B. 

REAGENTS. 
AIR ANALYSIS. 

Barium Hydroxide. — A solution containing about 4 grams 
of BaO to the liter. (1 c.c. = 1 mg. C0 2 , approximately.) 

Sulphuric Acid. — Dilute 46.51 c.c. of normal sulphuric 
acid to one liter. (1 c.c. == 1 mg. C0 2 .) To standardize the 
solution measure 25 c.c. into a weighed platinum dish, add 
one drop of phenolphthalein solution and titrate with the 
barium hydroxide to a faint pink. Evaporate to dryness on 
the water-bath, ignite, and weigh as barium sulphate. 

Standard Lime-water. (For Popular Tests.) — Shake one 
part of freshly slaked lime with 20 parts of distilled water for 
twenty minutes and let the solution stand overnight or until 
perfectly clear. This solution should be very nearly equiva- 
lent to the above standard sulphuric acid. Now to a liter of 
distilled water add 10 c c. of a solution of 0.7 gram of 
phenolphthalein in 100 c.c. of 50 per cent, alcohol and add 
lime-water drop by drop until a slight permanent pink color 
is produced. Add 12.6 c.c. of the above calcium hydroxide 
solution. The resulting solution is the standard lime-water 
used for the tests. 

WATER ANALYSIS. 

For Ammonia. — Water Free from Ammonia. — The am- 
monia-free water used in this laboratory is made by redis- 
tilling distilled water from a solution of alkaline permangan- 

204 



APPENDIX B. 



205 



ate in a steam-heated copper still. The apparatus used is 
shown in Fig. 10. Only the middle portion of the distillate 
is collected. Oftentimes the distillate from a good spring- 
water may be used. 

Nessler's Reagent. — Dissolve 61.750 grams KI in 250 c.c. 
distilled water and add a cold solution of HgCl 2 which has 
been saturated by boiling an excess of the salt and allowing 
it to crystallize out. Add the HgCl 2 cautiously until a slight 
permanent red precipitate (Hgl 2 ) appears. Dissolve this 




Fig. 10. — Still for Ammonia-free Water. 



slight precipitate by adding 0.750 gram powdered KI. Then 
add 150 grams of KOH dissolved in 250 c.c. of water. Make 
up to the liter and allow it to stand overnight to settle. This 
solution should give the required color with ammonia within 
five minutes, and should not precipitate within two hours. 

Alkaline Permanganate. — Dissolve 233 grams of the best 
stick potash in 350 c.c. of distilled water. Filter this strong 



206 APPENDIX B. 

solution, if necessary, through a layer of glass wool on a por- 
celain filter-plate. Dilute with 700 to 750 ex. of distilled 
water to a sp. gr. of 1.125, add 8 grams of potassium per- 
manganate crystals, and boil down to the original volume to 
free the solution from nitrogen. Each new lot of reagent 
must be tested before being used, but when the chemicals 
used are all good there should be no correction needed for 
ammonia in the solution. 

Standard Ammonia Solution. — Dissolve 3.8215 grams 
chemically pure NH 4 C1 in a liter of water free from ammo- 
nia. This is the strong solution from which the standard 
solution is made by diluting 10 c.c. to a liter with water free 
from ammonia. One c.c. of the standard solution = o.ooooi 
gram nitrogen. This solution, like the nitrite standard and 
other dilute solutions, must be preserved in sterilized bott.es 
protected from dust and organic matter. 

For Nitrites. — Standard Nitrite Solution. — The pure sil- 
ver nitrite used in making this solution is prepared by the 
double decomposition of silver nitrate and potassium nitrite, 
and repeated crystallizations from water of the rather diffi- 
cultly soluble silver nitrite. 1.1 grams of this silver nitrite 
are dissolved in nitrite-free water, the silver completely pre- 
cipitated by the addition of the standard salt solution used in 
the determination of chlorine, and the solution made up to 
1 liter. 100 c.c. of this strong solution are diluted to 1 liter, 
and 10 c.c. of this last solution again diluted to 1 liter. The 
final solution is the one used in preparing standards. 1 c.c. 
= 0.000000 1 gram nitrogen. 

Hydrochloric Acid. — 1 part of pure HC1 (sp. gr. 1.20) is 
diluted with three parts water. 

Sulphanilic Acid. — Dissolve 8 grams (Kahlbaum's) in 1 
liter of water. This is a saturated solution. 

Naphtylamine Hydrochloratc. — Dissolve 8 grams of a- 



APPENDIX B. 207 

naphtylamine in 992 c.c. of water and add 8 c.c. of strong 
HC1. (Keep in the dark.) 

Ilosvay's Modification. — (a) Sulphanilic Acid: Dissolve 0.5 
gram of sulphanilic acid in 150 c.c. of acetic acid, sp. gr. 1.04. 

(b) Naphtylamine Acetate: Boil 0.1 gram of ar-naphtyla- 
mine in 20 c.c. of water, filter through a plug ot washed ab- 
sorbent cotton, and add 180 c.c. of acetic acid, sp. gr. 1.04. 

For Nitrates. — Standard Nitrate Solution. — Dissolve 
0.720 gram of pure recrystallized KNO s in 1 liter of water. 
Evaporate 10 c.c. of this strong solution cautiously on the 
water-bath, moisten quickly and thoroughly with 2 c.c. of 
phenol-disulphonic acid, and dilute to 1 liter for the stand- 
ard solution. 1 c.c. = 0.000001 gram nitrogen. 

Phenol-disulphonic Acid. — Heat together 3 grams synthetic 
phenol with 37 grams pure, concentrated H 2 S0 4 in a boil- 
ing-water bath for six hours. 

For Kjeldahl Process. — Sulphuric Acid. — Sp. gr. 1.84. 
This should be free from nitrogen. May be obtained from 
Baker and Adamson, Easton, Pa. 

Potassium Hydroxide. — Dissolve 350 grams of the best 
stick potash in 1.25 liters of water and boil down to some- 
thing less than a liter with 3 grams of permanganate crystals. 
When cold, dilute to a liter with water free from ammonia. 

For Chlorine. — Salt Solution. — Dissolve 16.48 grams of 
fused NaCl in a liter of distilled water. For the standard so- 
lution dilute 100 c.c. of this strong solution to 1 liter. 1 c.c. 
= 0.00 1 gram chlorine. 

Potassium Chr ornate. — Dissolve 50 grams neutral K 2 Cr0 4 
in a little distilled water. Add enough AgNO s to produce a 
slight red precipitate. Filter and make the filtrate up to a 
liter with water free from chlorine. 

Milk of Alumina for Decolorization. — Dissolve 125 grams 
of potash or ammonia alum in a liter of distilled water. Pre- 



208 APPENDIX B. 

cipitate the Al(OH) 3 by the cautious addition of NH 4 OE 
Wash the precipitate in a large jar by decantation until free 
from chlorine, nitrites, and ammonia. 

For Hardness. — Standard Calcium Chloride Solution. — 
Dissolve 0.200 gram of pure Iceland spar in dilute HC1, tak- 
ing care to avoid loss by spattering, and evaporate to dryness 
several times, to remove the excess of acid. Dissolve the 
calcium chloride thus formed in i liter of water. 

Standard Soap Solution. — Dissolve ioo grams of the best 
white, dry castile soap In a liter of 80 per cent, alcohol. Of 
this strong solution dissolve 75-100 c.c. in a liter of 70 per 
cent, alcohol. This solution must have 70 per cent, alcohol 
added to it until 14.25 c.c. of it give the required lather with 
50 c.c. of the above CaCl 2 solution. 

Erythrosine Indicator. — Dissolve 0.1 gram of erythrosine 
in 1 liter of water. 

For Iron. — Standard Iron Solution. — Dissolve 0.86 gram 
of ferric ammonium alum, (NH 4 ) 2 S0 4 .Fe 2 (S0 4 ) 3 .24H 2 0, or 
a corresponding amount of the potassium salt in 500 c.c. of 
water, add 5 c.c. HNO s (1.20), and dilute to 1 liter. 1 c.c. = 
0.001 gram Fe. 

Potassium Sulphocyanide. — 5 grams per liter. 

Hydrochloric Acid. — 1 part HC1 (sp. gr. 1.20) to 1 part of 
water. 

Potassium Permanganate. — 5 grams KMn0 4 in 1 liter of 
water. 

For Dissolved Oxygen.— 

(a) 48 grams of MnS0 4 .4H 2 in 100 c.c. of water. 

(b) 360 grams of NaOH and 100 grams of KI in 1 liter 
of water. 

(c) HC1, sp. gr. 1.20. 

Sodium Thiosidphate Solution. — Dissolve 25 grams of pure 
recrystallized sodium thiosulphate in 1 liter of water. Dilute 



APPENDIX B. 209 

ico c.c. to i liter and standardize against a known K 2 Cr 2 7 
solution. 

For Lead. — Standard Lead Solution. — To a strong solu- 
tion of lead acetate add a slight excess of H 2 S0 4 , filter off 
and wash the precipitate. Dissolve it in ammonium acetate 
solution, made by neutralizing glacial acetic acid with strong 
ammonia. Make up to a known volume and determine the lead 
in an aliquot part by precipitating with K 2 Cr 2 7 and weigh- 
ing the lead chromate. Dilute an aliquot part to make a con- 
venient standard, say about 1 c.c. = 0.001 gram of Pb. 

FOOD ANALYSIS. 

For Milk Analysis. — Gasolene (Petroleum Ether). — Gaso- 
lene, sp. gr. 86° B., which leaves no residue upon evaporation 
at 6o° F. 

Fehling's Solution. — (a). Dissolve 69.28 grams of C.P. 
crystallized copper sulphate, carefully dried between blotting- 
paper, in 1 liter of water and add 1 c.c. of strong sulphuric 
acid. 

(b) Dissolve 346 grams of sodium potassium tartrate and 
80 grams of sodium hydroxide in 1 liter of water. 

Potassium Ferrocyanide. — Dissolve 1 part in 50 parts of 
water. 

Acid Mercuric Nitrate. — Dissolve mercury in double its 
weight of nitric acid (sp. gr. 1.42) and dilute the solution with 
five times its volume of water. 

Fnchsin Sulphurous Acid. — Dissolve 1 part of a rosaniline 
salt in. 1000 parts of water and add enough strong sulphurous 
acid to destroy the red color on standing. 

For Butter Analysis. — Pumice. — Bits of ignited pumice, 
about the size of a pea, dropped while hot into water and 
bottled for use. 



210 APPENDIX B. 

Alcohol (for Reichert-Meissl method). — 95 per cent, alco- 
hol redistilled from potassium hydroxide. 

Potassium Hydroxide (for Reichert-Meissl method). — One 
part good quality caustic potash dissolved in one part of 
water. 

Glycerine-soda (for Leflman-Beam method). — Add 20 c.c. 
of a 50 per cent, solution of sodium hydroxide to 180 c.c. of 
pure concentrated glycerine. The soda must be as nearly 
free from carbonate as possible. 

Iodo-mercuric Solution. — Dissolve 25 grams of iodine in 
500 c.c. of 95 per cent, alcohol; dissolve also 30 grams of 
mercuric chloride in 500 c.c. of 95 per cent, alcohol. Mix the 
two solutions and filter after standing 24 hours. 

Potassium Iodide. — Dissolve 150 grams of potassium 
iodide in 1 liter of water. 

For Cereals. — Anhydrous Ether. — Wash ordinary ether 
several times with distilled water and add solid caustic potash 
until most of the water has been removed. Then add small 
pieces of clean metallic sodium until there is no further evolu- 
tion of hydrogen gas. The ether thus prepared should be 
kept over metallic sodium and the bottle should be only 
lightly stoppered, in order to allow of the escape of any accu- 
mulated gas. 

Potassium Sulphide. — Dissolve 40 grams of the crystal- 
lized salt in 1 liter of water and filter. 

Potassium Hydroxide (for Kjeldahl process). — Sp. gr. = 
1.25. Dilute a liter of this solution to about 1.25 liters and 
boil down to something less than a liter with 3 grams of po- 
tassium permanganate. When cold dilute to a liter. 

Phospho-tungstic Acid. — Dissolve 50 grams of the crystal- 
lized acid in dilute hydrochloric acid, containing 25 grams of 
HC1 to the liter. 

Basic Lead Acetate. — Boil for half an hour 440 grams of 



APPENDIX B. 2 11 

lead acetate and 264 grams of litharge in 1500 c.c. of water. 
Cool and dilute to 2 liters. Allow to settle and siphon off the 
clear liquor. (Sp. gr. about 1.27, containing about 35 per 
cent, of the basic salt.) 

Millon's Reagent. — Dissolve mercury in twice its weight of 
nitric acid (sp. gr. 1.42) and dilute the solution obtained with 
three times its volume of water. 



BIBLIOGRAPHY. 



The following list comprises some of the more important 
works bearing on the subjects treated in the preceding pages. 
A bibliography of the chemistry of foods complete to 1882 
may be found in the Second Annual Report of the New 
York State Board of Health, and more or less complete 
bibliographies are to be found in Sadtler's "Industrial Or- 
ganic Chemistry " and Blyth's " Composition and Analysis 
of Foods." 

AIR. 

Air and Rain. R. Angus Smith. Longmans, Green & Co. London. 1872. 

Air and Its Relations to Life. Walter N. Hartley. D. Appleton & Co. 
New York. 1875. 

Report on the Air of Glasgow. E. M. Dixon. Robert Anderson. Glas- 
gow. 1877. 

Recherches sur l'Air Confine. A. Braud. Bailliere et Fils. Paris. 1880. 

Air Analysis. J. A. Wanklyn and W. J. Cooper. Kegan Paul, Trench, 
Triibner & Co. London. 1890. 

Les Poisons de l'Air. N. Grehaut. Bailliere et Fils. Paris. 1890. 

Treatise on Hygiene and Public Health. Vol. I. Thomas Stevenson and 
S. F. Murphy. Blakiston, Son & Co. Phila. 1892. 

Air and Water. Vivian B. Lewes. Methuen & Co. London. 1892. 

Methods for the Determination of Organic Matter in Air. D. H. fiergey. 
Smithsonian Institution. Washington, D. C. 1896. 

The Detection and Measurement of Inflammable Gas and Vapor in the 
Air. Frank Clowes. Crosby, Lockwood & Son. London. 1896. 

VENTILATION. 

Heating and Ventilation of the New Building, Mass. Inst. Tech. S. H. 
Woodbridge. Tech. Quart., 2, 76. 1888. 

213 



214 BIBLIOGRAPHY. 

Heating and Ventilation. J. S. Billings. Sanitary Engineer. New York. 

1893. 
Heating and Ventilating Buildings. Rolla C. Carpenter. John Wiley & 

Sons. New York. 1895. 

WATER. 

Report of the Royal Commission on Water Supply. Great Britain Par- 
liamentary Documents. London. 1869-70. 

Sixth Report of Rivers Pollution Commission, Great Britain. London. 
1876. 

Potable Waters. C. Ekin. 1880. 

Water Supply (Considered mainly from a Chemical and Sanitary Stand- 
point). W. R. Nichols. John Wiley & Sons. New York. 1883. 

Water Analysis for Sanitary Purposes. E. Frankland. John Van Voorst. 
London. 1S90. 

The Organic Analysis of Potable Waters. J. A. Blair. 1890. 

Drinking Water and Ice Supplies. T. Mitchell Prudden. G. P. Putnam 
& Sons. New York. 1891. 

Potable Water. Floyd Davis. Silver, Burdett & Co. New York. 1891. 

The Action of Water on Lead. John Henry Garrett. H. K. Lewis. 
London. 1891. 

Treatise on Hygiene and Public Health. Vol. I. Thomas Stevenson and 
S. F. Murphy. Blakiston, Son & Co. Phila. 1892. 

Examination of Water for Sanitary and Technical Purposes. Henry 
Leffman. Blakiston, Son & Co. Phila. 1895. 

Water Supply (Considered Principally from a Sanitary Standpoint). W, 
P. Mason. John Wiley & Sons. New York. 1896. 

Water Analysis. J. A. Wanklyn and E. T. Chapman. Tenth Ed. Kegan 
Paul, Trench, Triibner & Co. London. 1896. 

Water and Water Supplies. John C. Thresh. Rebman Pub. Co. Lon- 
don. 1896. 

A Simple Method of Water Analysis. John C. Thresh. J. & A. Churchill. 
London. 1898. 

Examination of Water (Chemical and Bacteriological). William P. Mason. 
John Wiley & Sons. New York. 1899. 

The Microscopy of Drinking Water. Geo. C. Whipple. John Wiley & 
Sons. New York. 1899. 

Micro-Organisms in Water. Percy F. Frankland and Mrs. Percy F. Frank* 
land. London. 1894. 

Mikroskopische Wasseranalyse. Carl Mez. J. Springer, Berlin. 1898. 

Water Softening and Scientific Filtration. Walter George Atkins. E. & 
F. N. Spon. London. 1880. 

Sewage Disposal in the United States. Geo. W. Rafter and M. N. Baker. 
D. Van Nostrand & Co. New York. 1894. 

Les Eaux-d'Alimentation, Epuration, Filtration, Sterilization. Edm. 
Guinochet. Bailliere et Fils. Paris. 1894. 



BIBLIOGRAPHY. 215 

The Filtration of Public Water Supplies. Allen Hazen. John Wiley & 

Sons. New York. 1895. 
Sewage Disposal on the Farm and Protection of Drinking Water. Theo- 
bald Smith. U. S. Dept. Agr., Farmers' Bull. 43. 1896. 
Water and Its Purification. Samuel Rideal. London. 1897. 
Water Purification at Louisville, Ky. Geo. W. Fuller. D. Van Nostrand 

Co. New York. 189S. 
Report on Water Purification at Cincinnati, O. Geo. W. Fuller. Board 

of Trustees, Cincinnati. 1899. 
Report of Filtration Commission, Pittsburgh, Pa. 1899. 
National Board of Health Report for 1882. 
State Board of Health Reports for Massachusetts, Michigan, Illinois, Ohio. 

The Mass. Reports, for 1872-75 and 1890-1900, especially, contain 

many valuable papers, the following being some of the most important 

of them : 
Chemical Examination of Water and Interpretation of Analyses. Thomas 

M. Drown. Rep. Mass. State Board of Health, 1892, 319. 
Discussion of Special Topics Relating to the Quality of Public Water Sup- 
plies. F. P. Stearns and T. M. Drown. Rep. Mass. State Board of 

Health, 1890, 717. 
On the Amount of Dissolved Oxygen contained in Waters of Ponds and 

Reservoirs at Different Depths. Thomas M. Drown. Rep. Mass. 

State Board of Health, 1891, 373. 
On the Amount of Dissolved Oxygen contained in Waters of Ponds and 

Reservoirs at Different Depths in Winter Under the Ice. Thomas M. 

Drown. Rep. Mass. State Board of Health, 1892, 333. 
On the Mineral Contents of Some Natural Waters in Mass. Thomas M. 

Drown. Rep. Mass. State Board of Health, 1892, 345. 
The Effect of the Aeration of Natural Waters. Thomas M. Drown. Rep. 

Mass. State Board of Health, 1891, 385. 

In addition to the above the following papers contain 
much information of value on special topics relating to water 
supply and water analysis : 

Chemical Examination of Drinking Water. Thomas M. Drown, Proc. 
Soc. Arts., M. I. T., 1887-8, 87. 

The Analysis of Water— Chemical, Microscopical, and Bacteriological. 
Thomas M. Drown. J. N. E. Water Works Assoc, 4 (1889), 79. 

On the Loss on Ignition in Water Analysis. Thomas M. Drown. Tech- 
Quart., 2 (1888), 132. 

The Odor and Color of Surface Waters. Thomas M. Drown. Tech, 
Quart., 1 (1888), 250. 

Reduction of Nitrates by Bacteria. Ellen H. Richards and George W. 
Rolfe. Tech. Quart., 9 (1896), 40. 

The Purification of Water by Freezing. Thomas M. Drown. J. N. E. 
Water Works Assoc, 8 (1893), 46. 



2l6 BIBLIOGRAPHY. 

The Filtration of Natural Waters. Thomas M. Drown. J. of the Assoc, 
of Eng. Soc, 9 (1890), 356. 

FOOD. 

The list given here is limited to books published since 
1890. 

Traite General d'Analyse des Beurres. A. J. Zune. H. Lamartin. 

Paris. 1892. 
Analyse des Matieres Alimentaires et Recherche de Leur Falsifications. 

Ch. Girard et A. Dupre. Vve. Ch. Dunod & P. Vicq. Paris. 1894. 
Animal and Vegetable Oils, Fats, Butters and Waxes. C. R. Alder 

Wright. Griffin & Co. London. 1894. 
A Handbook of Industrial Organic Chemistry. S. P. Sadtler. J. B. 

Lippincott Co. Phila. 1895. 
Chemistry of Wheat, Flour, and Bread. Wm. Jago. Simpkin Marshall. 

London. 1895. 
Foods : Their Composition and Analysis. Alexander W. Blyth. Griffin 

& Co. London. 1896. 
Analysis of Milk and Milk Products. Henry Leffman and William Beam. 

Blakiston, Son & Co. Phila. 1896. 
The Analysis of Food and Drugs. Part I : Milk and Milk Products. T. 

H. Pearmain and C. G. Moor. Bailliere, Tindall & Cox. London. 

1897. 
Principles and Practice of Agricultural Analysis. Harvey W. Wiley. 

Chem. Pub. Co. Easton, Pa. 1897. 
Testing Milk and Its Products. E. H. Farrington and F. W. Woll. Men- 

dota Book Co. Madison, Wis. 1898. 
Chemical Analysis of Oils, Fats, and Waxes. J. Lewkowitsch. Mac- 

millan & Co. London. 1898. 
Commercial Organic Analysis. A. H. Allen. Third Ed. Rev. by H. 

Leffman. Blakiston, Son & Co. Phila. 1898. 
Die Untersuchung landwirtschaftlich und gewerblich wichtiger Stoffe. 

J. Konig. Paul Parey. Berlin. 1898. 
Our Secret Friends and Foes. Percy Frankland. London. 1893. 
Die Menschlichen Nahrungs-u. Genussmittel. J. Konig. Julius Springer. 

Berlin. 1893. 
Foods and Dietaries. R. W. Burnet, M.D. P. Blakiston, Son & Co. 

Phila. 1893. 
Food and Its Functions. James Knight* Blackie & Son. London. 1895.- 
The Food Products of the World. Dr. Mary E. Green. The Hotel 

World. Chicago. 1895. 
The Story of Germ Life. H. W. Conn. Appleton & Co. New York. 

1897. 
The Relation of Food to Health. George H. Townshend. Witt Publish- 
ing Co. St. Louis. 1897. 



BIBLIOGRAPHY. 21? 

Food Materials and Their Adulterations. Ellen H. Richards. Home 

Science Pub. Co. Boston. 1898. 

Plain Words About Food. The Rumford Kitchen Leaflets. Ellen H. 

Richards, Ed. Home Science Pub. Co. Boston. 1899. 

The following bulletins of the United States Department 
of Agriculture will also be found useful for study or reference 
on the general question of food: 

Office of Experiment Stations, Bulletins. 
No. 9. Fermentations of Milk. 1892. 

11. Analyses of American Feeding Stuffs. 1892. 
21. Chemistry and Economy of Food. 1895. 
25. Dairy Bacteriology. 1895. 

28. (Rev. Ed.) Chemical Composition of American Food Materials. 

1895. 

29. Dietary Studies at the University of Tennessee. 1896. 

31. " " " " " Missouri. 1896. 

32. " " " Purdue University. 1896. 

34. Carbohydrates of Wheat, Maize, Flour, and Bread. 1896. 

35. Food and Nutrition Investigations in New Jersey. 1896. 

37. Dietary Studies at the Maine State College. 1897. 

38. " " — Food of the Negro in Alabama. 1897. 
40. " " in New Mexico. 1897. 

43. Composition and Digestibility of Potatoes and Eggs. 1897. 

44. Metabolism of Nitrogen and Carbon in the Human Organism. 1897. 

45. A Digest of Metabolism Experiments. 1897. 

46. Dietary Studies in New York City. 1898. 

52. Nutrition Investigations in Pittsburgh, Pa. 1898. 

53. " at the University of Tennessee. 1898. 

54. " in New Mexico. 1898. 

55. Dietary Studies in Chicago. 1898. 

63. Experiments on the Conservation of Energy in the Human Body. 
1899. 

66. Creatin and Creatinin. 1899. 

67. Bread and Bread Making. 1899. 

69. Experiments on the Metabolism of Matter and Energy in the 

Human Body. 1899. 
71. Dietary Studies of Negroes. 1899. 
75. " " " University Boat Crews. 1900. 

Division of Chemistry \ Bulletins. 
No. 13. Foods and Food Adulteration — (Nine Parts). 1SS7-98. 

45. Analyses of Cereals. 1895. 

46. Official Methods of Analysis. 1895. 
50. Composition of Maize. 1898. 



2 18 BIBLIOGRAPHY. 

Farmers' Bulletins, 
No. 23. Foods : Nutritive Value and Cost. 1894. 
29. Souring of Milk. 1895. 
34. Meats: Composition and Cooking. 1896. 
74. Milk as Food. 1898. 
85. Fish as Food. 1898. 
93. Sugar as Food. 1899. 
112. Bread and the Principles of Bread Making. 1900. 



INDEX. 



PAGE 

Acceptable water, requirements for 68 

Acid, benzoic, in milk 169 

, boric, in milk, detection of 168 

, carbonic, in water, estimation of in 

, hydrochloric, reagent for iron determination 208 

" nitrite test 206 

mercuric nitrate, reagent 209 

, phenol-disulphonic, reagent 207 

, salicylic, in milk, detection of 168 

"wine, " " 193 

, sulphanilic, reagent for nitrite test 206, 207 

, sulphuric, " " air analysis 204 

" " Kjeldahl process 207 

Acidity of milk, determination of 151 

Acids, in beer, " 193 

, in wine, " 191 

Adamkiewicz reaction 186 

Adams' method for fat in milk 154 

Adulterants in milk 166 

Adulteration, definition of 137 

, extent of 139 

, special cases of 141 

Air, carbon monoxide in 16 

, dust in iS 

, expired, composition of 10 

, importance of 3 

, inspired, composition of 10 

, organic matter in 41 

, water- vapor in 14 

Albumin, in milk, determination of 165 

Albuminoid ammonia, determination of S6 

, relation to organic nitrogen 94 

219 



2 20 INDEX. 

FAGE 

Alcohol, i»n liquors, determination of 190, 193 

, reagent for butter analysis 210 

, tables for calculating from specific gravity 202 

Alkaline permanganate, reagent 205 

Alkalinity of milk, determination of 152 

water, " 105 

Alum, in water, estimation of 117 

Amides, in wheat, determination of 187 

Ammonia-free water, reagent 204 

Ammonia, standard solution 206 

Aniline colors, in milk, detection of 167 

Annatto, in milk, detection of 167 

Aqueous vapor, table of tension of 195 

Ash, in liquors, determination of 191, 193 

of cereals, " 183 

milk, composition of 1 54 

.determination of 153 

Babcock method for fat in milk 156 

Barium hydroxide, reagent for air analysis 204 

Basic lead acetate, reagent 210 

Beer, examination of 193 

■' Behavior on ignition " of water residues 103 

Bibliography 213 

Biological examination of water 116 

Biuret reaction 185 

Brook-water, characteristics of 72 

Butter, "aroma" of ; 171 

, complete analysis of 181 

, composition of 169 

Butter-fat, composition of 170 

, examination of 171 

, rancidity of 171 

Calcium chloride, standard solution of 208 

Cane-sugar, in milk, detection of 166 

Caramel, in milk, detection of 167 

Carbohydrates, food value of 127 

in cereals, estimation of iSS 

Carbonaceous matter, in water, estimation of 98 

Carbon dioxide a disturbing factor 12 

in air, determination of 27 

in water, determination of in 

, essential property of 21 

, weight of cubic centimetre of , 196 

monoxide, in air, detection of 38 



INDEX. 221 

PAGE 

Carbon-monoxide, in air, determination of 39 

, presence of „„ ..,,,.. 16 

Casein, in milk, determination of , 165 

Cazeneuve reaction !q 2 

Cereals, analysis of !g 2 

, composition of , !3 

Chlorine, in water, determination of 99 

in well-water , 78 

, source of normal 59 

Clark's method for hardness of water 103 

Cohen and Appleyard method for carbon dioxide 33 

Collection of water samples „ k 82 

Color of waters, estimation of 1 n 

, source of 58 

standards for water analysis in 

Coloring-matters, in butter, detection of 181 

, in milk, " "..... 167 

, in wine, " " 192 

Cream, in milk, estimation of 150 

" Crowd-poison " 18 

Cycle of nitrogen , 53 

Defren's method for milk-sugar 163 

Dietaries . . 132 

Dissolved oxygen, in water, determination of 107 

Dust, in air, estimation of 42 

, presence of 18 

Edestin, in wheat, determination of 187 

Erythrosine, reagent for water analysis 208 

Ether, anhydrous, reagent , 210 

Expired air, composition of. 10 

Extract, in liquors, determination of 191, 193 

Extraction apparatus for fat in milk , 156 

Fat, in milk, methods for estimation of 154 

Fats and oils, in cereals, estimation of i»3 

, food value of 126 

Fehhng's solution, reagent for sugars 209 

Fibre, crude, determination of 189 

Filtration 74 

Fitz's method for carbon dioxide 35 

Fixed acids in butter, estimation of 174 

Food, chief dangers in use of 142 

, definition of 123 

, necessity for examination of 6 



222 INDEX. 

PAGE 

Food, importance of 5 

, methods of analysis of 146 

principles ■. 124 

, sanitary aspect of . . 7 

values, necessity for knowledge of 133 

, variation in nitrogen content 7 

Food-materials, one hundred common 130 

Formaldehyde, in milk, detection of 168 

Formulae for milk analysis 159 

Free ammonia, in water, determination of 86 

Fuchsine, in wine, detection of 192 

Fuchsin-sulphurous acid, reagent , 209 

Gasolene, reagent ^ 209 

Gliadin, in wheat, determination of 187 

Glutenin, in wheat, determination of 187 

Glycerine-soda, reagent for butter analysis 210 

Ground-water, history of 50 

Hardness of water, determination of 103 

, table for 200 

Heat of combustion 128 

Hehner's method for butter analysis. 174 

hardness of water 105 

Hiibl method for butter analysis 175 

Ice, rules for use of.".:; 60 

Ilosvay's method for nitrites in water 95 

Inspired air, composition of. . to 

Iodine value, in butter, determination of 175 

Iodo-mercuric solution, reagent , . . . 210 

] ron, in water, determination of 106 

, standard solution for water analysis 208 

Kjeldahl method for nitrogen , 92, 183 

, how modified for nitrates 185 

, theory of 184 

Kubel's method for " oxygen consumed " 98 

Lake-water, characteristics of 72 

Lead, in water, determination of 118 

, standard solution for water analysis 209 

Leff man-Beam method for butter analysis 174 

Leucosin, in wheat, determination of 187 

Liebermann's test 186 

Lime-water, standard for air analysis 204 



INDEX. 223 

PAGE 

Liquors, fermented, examination of igo 

"Loss on ignition" in water analysis 101 

** Luftprufer," Wolpert's 37 

Malt extract, preparation of 189 

Manganous sulphate, reagent for oxygen 208 

Mechanical ventilation, principles of 23 

Melting-point of butter, determination of 178 

Micro-organisms, in air, estimation of 40 

Microscopic examination of butter 177 

Milk, fermentations of 148 

" Milk of alumina," reagent for water analysis 207 

, percentage composition of 147 

, reaction of 151 

Milk-scale, Richmond's 160 

Milk-sugar, determination of 161 

, optical determination of 164 

Millon's reaction „ 186 

reagent, preparation of 211 

Mineral salts, in food, importance of 128 

, in water 59 

, presence of, in potable water. 79 

Moisture, in cereals, determination of 182 

Muscular activity and respiratory exchange 15 

Naphtylamine acetate, reagent 207 

hydrochlorate, reagent -. . . 206 

Natural ventilation, principles of 22 

Nessler's reagent, preparation of 205 

Nitrate, standard solution for water analysis 207 

Nitrates, in water, determination of 96 

Nitrite, standard solution for water analysis 206 

Nitrites, in air, determination of 39 

, in water, determination of 94 

Nitrogen essential to living matter 63 

, cycle of 53 

, in beer, determination of 193 

, in well-water 77 

Nitrogenous compounds, why dangerous 64 

matter, results of decay of 64 

substances, importance of 125 

Normal waters, table of . . . , 19S 

Nutritive ratio 129 

Odor of water, analytical value of 74 

, detection of . . . • 114 



224 INDEX. 

rAGE 

Opacity of milk, measurement of 150 

Organic carbon in water 65. 

matter, in air, determination of 41 

nitrogen, in water, determination of 92 

Organisms in water, work of 55 

Orseille, in wine, detection of 192 

" Oxygen consumed," determination of 98 

Oxygen dissolved in water, determination of 107 

, table of saturation 200 

Pettenkofer method for carbon dioxide 28 

Phospho-tungstic acid, reagent 21a 

Physical methods of butter analysis. 177 

Polluted waters, examples of 199 

Popular tests for carbon dioxide 33 

Potassium chromate, reagent for water analysis 207 

ferrocyanide, reagent for water analysis 209 

. hydroxide, reagent for butter analysis 210 

, for Kjeldahl method 207, 210 

iodide, reagent for butter analysis 210 

dissolved oxygen 208 

permanganate, reagent for iron 208 

sulphide, reagent 210 

sulphocyanide, reagent for iron 208 

Predigested foods . 138 

Preservatives in milk 168 

Pressure, influence on respiratory exchange , 12 

Problem of safe water 62 

Proteids, in cereals, determination of total 183 

milk, determination of total 165 

, qualitative tests for « . . . 185 

, separation of. . .-. 186 

Pumice for butter analysis 209 

" Purified " water, definition of 57 

' ' Radiator " for igniting water residues 101 

Reaction of milk 151 

Refractive index of butter, determination of 178 

Reichert-Meissl number, determination of 172 

Relation of water to health 52 

Residue, in water, determination of 101 

Respiratory exchange, explanation of 10 

quotient 14 

River-water, characteristics of 73 

Salt, in butter, determination of 181 

, in milk, determination of 166 

Sanitary chemistry, scope of 1 



INDEX. 225 

PAGE 

Sanitary science, importance of , 2 

water analysis, principles involved in. 66 

Saponification of butter- fat 173 

Sediment, in water, estimation of 116 

Sewage, typical analyses of igg 

Shallow wells, characteristics of water from 77 

Soap, standard solution for water analysis 208 

Sodium carbonate, in milk, detection of , 169 

chloride, standard solution for water analysis 207 

Sodium hydroxide, reagent for dissolved oxygen. . . . , 208 

thiosulphate, reagent for dissolved oxygen „ 208 

Soot, in air, estimation of 42 

Sophistication, meaning of , 137 

Specific gravity of butter, estimation "of 178 

of milk, estimation of 149 

, table for correcting 201 

Starch, in cereals, determination of 188 

milk, detection of 166 

Statement of results in water analysis ng 

Storage of water, results of 57 

Sucrose, in milk, detection of , 166 

Sugars, in cereals, determination of , 188 

Surface water, characteristics of , 71 

, summary of 75 



Tension of aqueous vapor, table of 195 

Total solids, in milk, determination of 152 

Trade names 140 

Turbidity and sediment, cause of 74 

Turbidity of water, estimation of 116 



Ventilation, requirements of 26 

, to test efficiency of 24 

Vital capacity, definition of 10 

Volatile acids, in butter, determination of 172 

Water, added, determination of, in milk 166 

Water analysis, blank form for 120 

, limits of , 69 

, value of go 

, circulation of, on the earth 47 

, illustration of contamination of 4S 

, daily quantity needed 4 

free from ammonia, reagent 204 

, general use of 5 

in butter, determination of , , . , 178 

, legal restrictions upon use of . . . . , 43 



226 INDEX. 

PAGa 

Water, methods of analysis of 82 

, mineral contents of 199 

need of 4 

, preliminary inspection of source of 66 

, solvent power of 51 

, table of average composition of 197 

, the ideal drinking 45 

classification of 71 

Water-pipes, danger from 8o 

Water-vapor in air 14 

Well and spring waters, characteristics of 76 

Werner-Schmid method for fat in milk 157 

Wine, analysis of. . , 190 

, specific gravity of 190 

Winkler's method for dissolved oxygen in water 107 

Wolpert's method for carbon dioxide 37 

Xanthoproteic reaction 186 



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